Repair and Diagnosis of Problems with Your Imperial's Generator

Imperial Home Page -> Repair -> Electrical System -> Charging System -> Generator

General Definition and Tips from Dick:

A generator is simply a spinning armature inside a magnetic field. It has no smarts at all. It will produce current when it is spinning, and if the current has a place to go, it will go there. If it has no place to go, the voltage will build up to a high level. A "12" volt generator can produce up to 40 volts or so into an "open" circuit. The voltage regulator directs the current, prevents current from flowing backwards into the generator at low RPM, and adjusts the amount of current by adjusting the strength of the magnetic field. There is always some residual magnetism in the generator steel case, so a generator will begin to produce current even with no applied field current, thus you can "bump" start a car with a generator. The battery also participates in this regulation, by the fact that as the battery approaches full charge, the voltage on the battery terminal increases, thus placing more of an "obstacle" in the path of the current from the generator. The voltage regulator monitors this situation, and when the design level of voltage at the battery (typically 14.6 volts on a "12" volt battery) is reached, it reduces the magnetic field in the generator to near zero, so that only a trickle of charge reaches the battery. Even if there is no battery in the car at all, the car will run just fine, once you get it started, on the generator's output. Many times on old car tours, I have had to get someone with an inoperable generator going by swapping batteries with him, leaving my car idling with no battery until I install his old (dead) battery in my car to use and recharge for the day's touring. Next day we swap back again, letting my car do all the recharging for both vehicles. This trick will also work with an alternator setup. The only difference operationally with alternators is that they will not begin to produce electricity until an external source of current is provided to the field windings, thus the inability to bump start a totally dead car with an alternator.

More good tips and information from Dick:

The following will apply to any car (other than a Ford product) that does not have an alternator.  A generator is a series wound motor which consists of a rotating armature inside a fixed field. The rotating armature cuts the lines of magnetic flux created by the field, and from this action, produces an induced current in the armature windings. The current is harvested by the contacts to the armature. The contacts consist of a fixed pair of brushes that ride on the armature commutator. The polarity of the produced current alternates as the armature rotates, but the commutator segments are arranged such that the electrical contacts reverse polarity at the exact right instant to counteract the reversing polarity of the generated current, thus producing a fixed polarity "DC" output at the "A" terminal of the generator. The field winding must be allowed to conduct current or it will not produce a field, and the result is there will not be any output from the armature. Therefore, to test a generator you MUST ground the "F" terminal to the case (the third terminal you see) of the generator, and rotate the armature. A healthy generator will put out about 14 volt (12 volt system) at 800 engine RPM, if it is not connected to any load. Actually, if you see any voltage above 8 volts or so at engine idle on the "A" terminal, your generator is probably working just fine. This is only to see what happens for a minute or so; don't keep this temporary ground in place, it can cook your battery by overcharging it. If the generator passes this test, your problem is elsewhere.  The regulator is the next suspect. If the regulator is working properly, all it does is to ground the "F" terminal on the generator through one of a choice of 2 or 3 resistances, to control how much field current is allowed to circulate, and consequently how much amperage is generated by the generator. When the battery is low, the "F" terminal should be grounded through a very low resistance, and when the battery is up to fully charged, the "F" terminal is still grounded by the regulator, but through a 30 OHM or so resistance (12 volt system). Verify that the "F" terminal on the Generator is connected through to the "F" terminal on the regulator, and that the regulator itself is well grounded to its case. If both of these things are true, and you don't see a voltage on the generator output "A" terminal with the engine idling, your regulator is probably bad. (You never say "definitely" with electrical things.)  Further, on the regulator, if you do see voltage at the "A" terminal on the generator, verify that you see the same voltage at the "A" terminal on the regulator. If not, inspect the wire and connection. If so, then look at the "BAT" terminal on the regulator. It should also show the same voltage.  If not, your regulator is almost certainly bad, even though it passed the "F" grounding test. If you do see the generator output voltage at the BAT terminal of the regulator, yet the battery is still not being charged, there is a bad connection either in the wiring harness or at the ammeter (if so equipped), you'll just have to track it down by visual inspection or following the path through the maze of the wiring harness with your voltmeter. You'll need a wiring diagram to do this. 

Tip from Ken- Generator Polarizing 101: 

Most's only necessary to polarize a generator when it has been rebuilt, and when new pole shoes have been installed. It should have enough residual magnetism left to allow it to start charging in most other cases. To polarize a rebuilt generator mounted on the vehicle, disconnect the field wire and the battery wire from the regulator (notice it's done at the regulator not the generator). With the engine turned off, momentarily connect the two wires together. Do not polarize a generator by any method that applies battery voltage to the field terminal of the regulator, such as shorting from the battery terminal to the field terminal of the regulator, or by connecting a jumper wire directly from the battery to the generator field terminal. This causes excessive current to flow from the battery through the regulator contacts to ground, and burns the points. The terminals on the regulator should be marked F: field, G: ground, and B: battery. If they aren't marked on the regulator, you can trace them with a ohmmeter from the generator, where they should be marked in the same manner. If not, the the two wires that are on the side of the case are ground and field, the insulated terminal is the field coil wire, the uninsulated terminal is the ground. The other wire located in the back of the generator is the battery terminal.

How to reverse the polarity of your generator- by Dick:

What happens when the ground has been reversed on your battery?  It could possibly reverse the polarity of the generator (not the voltage regulator), and the way to reverse it back is to disconnect the armature and field windings on the generator and momentarily spark the armature terminal to the battery negative (hot) post. It will spark like crazy (if everything is OK with the generator), just tap it once. If the car still will not charge, you'll have to troubleshoot the regulator and generator. 

The following assumes that your car has an ammeter. If you have an idiot light only, the easy way to determine if it is charging is to turn on the parking lights and then with the car running at high idle, pull off one battery cable. If the engine stops, it ain't charging. If it keeps running, it is charging at least a little. To investigate if it is definitely not charging, follow the next steps. 

I'd perform step #1 before even bothering to repolarize the generator, because this will show you the problem in at least 75% of the cases of not charging. 

1.With the car running at high idle try grounding the field terminal (that's the small terminal on the generator, by the way, but you know this already, right?) on the generator (the smaller of the two terminals, or smallest of the three terminals if there's a case ground wire to the body somewhere). If that makes it charge like crazy, the problem is with the regulator or the wiring, and your generator is most likely OK. If it doesn't, disconnect the wire and turn the engine off, then repolarize the generator and try again. If it still won't charge, you still don't know much, so go to step two, but first, disconnect the temporary ground wire from the field terminal BEFORE you turn the engine off. 

2. Find the labels on the contacts of the regulator. The two with large wires on them will be labeled "B" and "A" most likely, for battery and armature. We definitely don't want to touch the "F" (field) wire at this time. If you can't read the labels (sometimes these are really obscure), trace out the wires. The "A" wire goes directly to the armature on the generator, while the "B" wire goes into the dash area, probably directly to the ammeter gauge. Again, with the car running at high idle, temporarily connect between these two terminals, with all the car's wires still hooked up. You may get a spark when you make the connection, but it won't hurt you, it's only 8 volts or so. If you get a spark when you connect these, it is indication that current is flowing, but you don't know if it's flowing in the right (charging) direction until you look at the gauge. If it is now charging, you've found your problem - your regulator cutout contacts are not closing, and your generator is probably OK. You should replace the regulator (NAPA still carries these, be sure you get a positive ground regulator!). If you don't get a spark, check the gauge anyway, you might have lucked out and connected it so cleanly that no spark was produced. If it is charging, we have the same result as before, it looks like your regulator is bad. If it is still not charging, note whether it is simply still at the center of the gauge, or reading a large discharge (a small discharge will be normal, but note if it is any more discharge than you were used to seeing before starting to investigate all this). If the gauge shows no change from last week, you still don't know, but we're getting close. Again, disconnect this added wire BEFORE you turn off the engine. Go to step #3 if there was no change on the gauge from step #2, to step #4 if there was a heavy discharge. Disconnect the wire quickly if this is happening! 

3. Now, put the engine at high idle again, and ground the field at the generator as in step one, then repeat step 2. If it now charges like crazy, you know that the problem is either with the regulator or the wiring, and that there is nothing wrong with the generator. If it still doesn't charge, the generator is probably not putting out, or possibly the "A" wire is broken somewhere between the regulator and the generator. Inspect and decide. If you have an Ohmmeter, disconnect one end of the wire and check it's resistance - should be zero, or very close. If it does charge like crazy, take the temporary grounding wire off the field terminal on the generator, and put it on the other end of the same wire, at the "F" terminal on the regulator. The result should be exactly as before, it should charge like crazy. If it doesn't, you've found part of your problem, the field wire is bad. Replace it. If it still won't charge, the regulator is also bad, replace it too. 

4. We got here because when you connected across the "cutout" contacts it discharged heavily. This means there is a problem with the generator, but it could be just a polarity problem. Polarize the generator, as described above, if you haven't yet done this. If you polarized it and it still discharges, you probably have a grounded armature in the generator. Find a generator shop. Bring money. You still don't know anything about your regulator, you may have to go down this path again when you get the rebuilt generator back from the shop, or you could just spring for the extra $35 and put a new regulator on it, then your only worry will be wiring. By the way, be sure the generator guy knows the generator is for a positive ground car, or else you'll have to go through the polarization dance all over again.

Tip from John:

I swapped out the dual point distributor on my '59 with a Mopar Performance electronic ignition kit and no problems even with the original generator and generator regulator setup. The instructions mention that the ignition voltage should not be less than 12.5V and I measured around 12.8V at idle with the head lights and blower motor on. Timing mark is rock steady at idle now. I have some pinging during acceleration so I have to retard the timing (I think I set it to 10 degrees BTDC with the vacuum advance disconnected). Any suggestion on what the retarded setting should be? The vacuum advance in the Mopar Performance distributor is adjustable and I've set in for minimum.

Tip from Dave:

Over the weekend I decided to have a go at repairing the field coil to the generator on my '60 LeBaron. For a few years I had been trying to get a replacement to go with the new ammature that I have. So a trip down to an auto electrical shop was in order. With taking the Imperial, I found that I would get a bit more response & sense from people in the trade. After a good discussion with the guy whom rebuilds alternators he advised me what basic materials I needed to do the job myself. This was a roll of Egyptian cotton about 3/4 inch wide to re-wrap the wire. Then a tin of Knotting sealer, which is in effect shellac! Knotting sealer is the stuff used as a pre-paint treatment on timber that is weeping sap. I must admit that my chin hit the floor when I found out that the repair would work out as cheap as it did, plus that regarding the wood knot sealer. The roll of cotton & the shellac will re-do all the electrical motors in the car at a cost if I convert it to U.S dollars, 15 bucks! Plus my spare time which I don't count.

Question from Luke (difference between alternator and generator):

Does anyone know the difference between a generator and an alternator and why 1960 Imperials with air-conditioning had an alternator? Just the continuing saga for my air-conditioning.


From Tony:

The Alternator was first used on 1960 Chrysler products - All Valiants had it, and as the year progressed, more and more Mopars had it installed as a mid-year change.  Alternators are MUCH BETTER than generators. They provide more charge for the system, even when the car is idling.

From Bob:

Generators deliver Direct Current, Alternators deliver Alternating Current. Since automobile electrical systems are DC, the alternators are equipped with rectifiers, (diodes), to convert the AC to DC.

From Brett:

Whether or not your car has an alternator depends on when it rolled down the assembly line. I would recommend however, if you're going to add factory A/C, change over to an alternator... (The blower motor pulls a lot of current) don't forget to change the voltage regulator as well.


My problem is the generator is not charging the battery.  Does anybody have any troubleshooting tips for repairing the generator?

Reply from Dick:

Both the generator and the regulator are really easy to diagnose and fix, and parts are available. To sort out which is giving problems, you are going to need some test clip leads, and a cheap VOM. Thus armed, and before you do anything else, polarize the generator. Do this by momentarily touching the battery hot lead to the armature terminal on the generator. 

By the way, are you sure you have the polarity right? I think these cars are positive ground. 

When you touch the battery to the armature, there will be a health spark. Don't worry, 6 volts will never hurt you, you can't even feel it, it just looks impressive. You only need a fraction of a second to polarize the generator, so just tap the wire to the terminal. 

Now, start the engine and have a helper observe the ammeter. With the engine at fast idle, momentarily ground the field terminal on the generator. The generator should produce voltage at the armature terminal, at least 7 volts or so. If it does, your generator is working. See if the ammeter shows charge under this condition. If it does, the problem is either with your regulator or with the wiring. More about this later. 

If the generator is NOT working in this test, turn everything off and remove the generator from the car, take it to the bench and inspect the brushes and the armature for cleanliness. 

Clamp the front housing end in a vise, remove the two long bolts from the rear of the case, and pull the rear end off, then remove the outer case/field assembly. 

If it needs new brushes, or the commutator is oily, take care of that first, it may be all you need to do. 

Clean the commutator with "Brake Cleaner", and spin it manually while you hold a strip of find sandpaper against the contact surface. If the mica is up level with the copper, groove it with a hacksaw blade so the brushes can make solid contact. If you need to replace the brushes, take the old ones to NAPA and let them match them up for you. While you have it apart, verify that there is no continuity from the commutator surface to the shaft. If there is continuity there, the armature will have to be rewound or replaced. (This is not usually the case.) Also verify that there IS continuity from any one segment of the commutator to all others. Again, if it fails this test, you need a new armature. This will be hard to find, but it is available. If your local generator shop doesn't know where, we'll help you find one. 

Also, check that there is continuity from the field brush terminal to the brush itself, and from the field terminal through the field windings in the outer case. If this fails, you need a new field, also not a common problem. 

Now you are ready to reassemble it. Do not over grease the rear bearing or over-oil the front bearing. A little dab'l do ya, here. 

Then retest it. You can just spin it by hand, CW from the front, and note any voltage generated at the armature terminal when the field terminal is grounded, using your VOM. This time we'll settle for any voltage at all, since you cannot spin it fast enough to get a real output. If you see the meter react at all to spinning the armature, put the generator back on the car and repeat the first test. If it still isn't putting out at least 7 volts at fast idle, it will have to be further investigated, and I recommend you take it to a professional. Pick someone who has been at it for years, so they know what a generator is. 

Now back to the wiring of the regulator. If the generator is now working, but still not charging the battery, try grounding the field wire at the regulator. This is the same wire we just grounded at the generator, and you should see the same result. If you don't, investigate the wire. 

If grounding the field wire made the generator put out, but it is still not getting to the battery as shown by the ammeter, probably you have a bad regulator. Possibly there is a problem with the armature wiring from the generator to the regulator, so check this. If you don't see anything wrong, and you measure continuity from the armature terminal on the generator to the "A" terminal on the regulator, I would take a chance and get a replacement regulator. Again, these are in stock at NAPA, just make sure they give you a positive ground 6 volt regulator. It may not look exactly like the original, but maybe after we know the new one is fixing your problem, you can decide whether or not to seek a NOS regulator, or change the case cover so it at least looks right. Often this is easy to do, and undetectable. It is important that the cover fit exactly the same, however, since it is part of the magnetic circuit of the regulator, and a wrong fit will affect the settings. 

Question from Sean:

I am in the process of rebuilding my generator.  I took the brush end plate off per the manual, and indeed, it looks like I need new brushes. The book says to replace at 5/8", and these eyeball at about 1/2". Also, there's a "chip" out of one of them, effectively reducing its surface area even more, I'm sure. I ordered an overhaul kit, and will give this thing the "once-over" when I get the parts. My only question is, how "clean" should this thing be on the inside. There was no splash guard on it, I almost never drive this thing in the rain, but I ordered one with the rebuild kit. The problem I have is that the generator looks pretty dirty inside. Not like, caked with mud, but some general greasy griminess all over. Is this a big concern, and should I do anything to try to "clean" the parts, like the armature, or would I be likely to do more harm than good.


From Tim:

The brushes should be available at any good auto parts store like NAPA. Re-installing them is quite easy and it should be fairly clean but no need to be fanatical.

From Bill:

Most likely what you are looking at for "dirt" is actually graphite dust from the wear of the brushes. This is not detrimental to the function of the unit, and I would leave well enough alone. Follow the directions in the service manual and you should be fine. As the brushes wear, the spring tension that holds them firmly against their contact point on the armature is lost, and as a consequence, power output wanes over a period of time.

Question from Dave (1954):

Our '54 Imperial (6 volt positive ground) has been acting up.  The car has a "AMP" light on the dash. Recently--but not predictability--this light will remain lit-up after the car has been turned off. This has happens every 1 in 25 times the car is driven. But, when it does occur, you know something is not good. It seems that the car is starting to burn up--with a slight electrical smell coming from the engine compartment. Each time we have quickly disconnected the battery. (I have put in a cut-off switch so it can be done very fast.) And, when we do this, we can hear the spring-loaded circuit breaker located in the front fender disengage. Then, when the battery is reconnected the car functions as if nothing has happened. This has occurred three times in the last two months. No pattern seems to be associated with these events. Do I have a problem with (1) my battery, (2) my generator, (3) my regulator (4) the circuit breakers, (5) unknown wiring short somewhere in the car? What suggestions do your have. Thank you for giving us some help.


From Dick:

Your regulator cutout contacts are sticking closed. The burning smell you detect is the windings in the generator. Disconnect the battery EVERY TIME you turn the car off until you correct the problem, or you will lose the generator and perhaps much more. 

You need to get a new regulator, don't fool around with trying to resurrect this one. Once they are worn out, nothing will make it reliable again but replacement. Last time I looked, NAPA still lists a 6 volt positive ground regulator, they may take a day or two to get it for you, but they have them, and the quality is good, I used them on my Packards all the time.

From Hubert:

I had a similar problem with my '55. I bought a new regulator from Kanter, and now, everything is working nice.

From Bob:

I had an old '50 Pontiac that did the same thing. The problem was the voltage regulator. The points in the regulator stick and when the key is turned off, there is in essence a dead short created. The cover can be removed from the regulator and the points filed but it is my opinion that it would be much better and safer to put on a new regulator. Remember to polarize your regulator/generator before you start the car. By the way, this was not an uncommon problem, I knew other guys that had the same thing happen to their cars (I used to work as a mechanic). I strongly suggest putting on a new regulator and see what happens. It can't hurt anything and you sure don't want to burn up any wiring.

Question from Mike (1955):

I have recently bought a 1955 Imperial. My first restoration project.  On more than one occasion I have needed a jump start. I have checked the battery, it's good. I have tightened the belts, some improvement.  The problem is the car is showing that it is discharging when the lights and wipers are on. Would I be correct to assume that the generator is not working correctly?


From Dick:

Generators have the limitation that they do not charge the battery unless the engine is turning at road speed. You cannot expect it to show a charge when the engine is idling. If, however, it continues to show a discharge when you rev the engine, you definitely have a problem with either the generator or the voltage regulator, or the wiring involved with them. 

Try to find an automotive electrical shop which has been in business for at least 60 years, and has a technician with gray hair and preferably, one who walks with the aid of a cane or walker. This person will do about 30 seconds of checking and tell you exactly what you need to replace. Do not let anyone start changing parts in the "hopes" that he will stumble on the correct culprit. This is a way for the shop to make money, but it is not a way to figure out what it wrong with your car.

From Hugh:

My advise is to get the generator checked and possibly rebuilt.

Question from Hubert (1955):

The generator of my '55 Imperial failed last Friday. A friend agrees to borrow me his '55 Desoto generator (with power steering output)

Do you know if '55 Imperial and '55 Desoto have the same generator/regulator assembly ??

Reply from Lew:

The part number for a 55 Desoto Generator w/ power steering is the same as that for a 55 Imperial w/ power steering. They should be marked 1604 843. Both are also indicated as 55 amps. The only issue you may have is the pulley assembly.

Question from Mike (1956):


Would someone in the OIC happen to know the proper Chrysler Part # and/or AC Delco Part # for the Generator in a 1956 IMPERIAL with AC and power steering?


From Philippe:

I've found two references (in 2 different books) for this generator:
- GJC 7006 (dual ball bearing) Chrysler # 1642009
- GJC 6003 (ball bearings at front and rear) Chrysler # 1704272

The two are 12 V 30 A generator.

From Roger:

The numbers on the generators on both my '56 Southhamptons w/A/C are as follows:

PN 1642007, Autolite # GJC 7003A

From Jeff:

While my car doesn't have AC, I do, by mistake, have the generator off an AC car operating in it. There are two identifying numbers on the dataplate which I just went and read:

Autolite part number: GHM 6003B
Part number (I'm assuming the Mopar #): 1704273

Question from Jeff (1956):

I discovered this afternoon while replacing belts on my '56 that the rear bolt holding the generator to the bracket has snapped. I'm guessing that this is
due in part to the fact that the generator appears to be about 1/2" too long for the bracket and not perfectly shimmed in place.

Are there alternate brackets available for the larger generator or shims that will fit properly or am I better off getting one of the shorter generators that I have in the parts bin rebuilt and installed?

Reply from Paul:

I don't think that you can easily adapt another generator to your car, Jeff. The power steering pump is attached to the back of the generator with a special rubber coupling. It is common for the bracket or the bolt, or both to fracture due to the extra stress and strain of the power steering pump being added to the generator. The bracket should be welded up if it needs repair and the bolt should be replaced. The brackets usually fracture where they fasten to the intake manifold.

Question from Tony (1956):

I put my kickboard back in place on the drivers side of my '56 imperial. There was a heavy gauge wire that grounded to the frame for a short while. I noticed the ammeter went way off of the discharge side of glass. I then looked in the engine compartment to see smoke coming out of the generator. I moved the wire from where it was grounded and the ammeter stays on the disscharge side even when I revved the engine. Have I fried something?

Reply from Dick:

Take the following steps immediately!!

Turn off everything in the car, and close the doors. Disconnect one battery cable (it doesnt' matter which one), then touch it to the battery post it came off to see if any spark occurs. If there is no spark, you're short has gone away. With the battery disconnected, tap on the face of the ammeter. It may be stuck from having been driven totally off scale. Tapping may bring it back to center. If not, you may have to replace it, but since you don't have a spark when you tap the cable on the post, you don't have a short, and you can safely drive the car that way - your ammeter is simply stuck and therefore its reading can be ignore.

IF, on the other hand, you do see a spark when you tap the cable (if your clock works, one spark on the first tap is OK, but that should not recurr for a few minutes when the clock needs to wind again), the spark indicates something is drawing current, and you should leave the battery disconnected until you find the short - leaving it connected will at the least ruin the battery, and at the worst, ruin your whole day by burning up the car and whatever building it is parked in.

Follow-up from Tim:

I just went outside and started her up. I remember reading somewhere if you un hook the battery cable while the car is running and it dies immediately something is no good. Is it the generator or regulator?

Reply from DeVere:

It is more clear to me to simply unplug one of the battery terminals and run a test light between the bat post and the disconnected cable end. If everything is off the light will be off. If you have a short or something is on the light will light indicating current. Simply start pulling fuses to look for a short in a system. You can set the light so you can see it between the hood and cowl of your Imperial. (Make sure the door is closed or you disable the interior light circuit, because it will light the test lamp, with the door open. I for one could never see that little spark at the cable. Do what works best for you. On the older cars, if you pull the Battery cable on a running car and it is idling correctly, it should stay running. If not you may need a regulator or a alternator/ generator. I would not do this on the newer computer cars because it may cause a voltage spike and damage things. (computer, regulator and such.) After thought.... if you are looking for something that is left on or on by accident, the light will light till you pull that systems fuse. Several times I found out that a glove box light was my battery drain!

Reply from Kerry:

Good technique DeVere. I knew that trick from years back but had forgotten it. Thanks for the reminder. Probably my most used tool is a collection of 'jumpers' made from lamp cord wire and alligator clamps. Some are short and some are 20' long. When I'm tracing a problem, I use the cables to bring the contact area to wherever I'm working. Using a small light bulb in a tail light socket with these jumpers would allow you to work under the dash and see immediately what the result was.

Reply from Dick:

Once you have cleared the short, the spark should be gone also. This episode shouldn't have hurt the voltage regulator, unless it was left connected for more than a minute or so with the current flowing. If it was left connected longer than that, the regulator may have been damaged, but the symptom will be that there is no charging going on. So if your tapping on the gauge brings it back to life, you can check for that. If the gauge stays stuck, you can always check for charging by starting the engine, then pulling off on battery cable. If the engine keeps running, the generator is charging, at least a little, so you know the regulator is somewhat functional.

Question from Anthony (1956):

Does anyone know where I can find the green generator tag that goes on a '56 Imperial generator?

Reply from Tony:

Jim Osborn Reproductions 

101 Ridgecrest Drive 

Lawrenceville, GA 



Question from John (1956):

Alternators on newer cars are rated at "X" amp alternators, does anybody have any idea if the older "generators" are rated the same, and if they are what is the rating for the one on my 56?  I have seen all of the traffic lately concerning "the right battery", etc., and I have just changed my battery from an 80 amp to a 100 amp battery to give me a greater starting shot.

Reply from Mike: 

The generator in a '56 Imp is rated at 30 amps (40 amps for the limo) @ 2100 rpm--not very high compared to today's alternators.

Question from Bob (1956):

I 'volunteered' to re-install a freshly rebuilt engine and transmission in a friend's 1956 Chrysler 300B. We got it running last weekend and show no charge on the dash ammeter at any RPM. The generator was rebuilt over the winter while the engine was out. The regulator was not touched, and had been working fine.  The service manual says to take a jumper from the field wire at the generator to ground to see if you then get charge. We did it and it did not charge. The manual then says to check the armature wire and the field wire to the regulator for continuity. Both wires are fine. All wires are 2 years old and check out with no shorts on the VOM.  The engine to chassis ground is new and strong. I was thinking perhaps we needed to re-polarize the regulator but we did not do that. As of now, we have the generator and regulator back to the repair shop so they can
check each. No word yet on their results.  Should we have re-polarized the regulator? But doesn't that mean you should have to do it after every long period of storage with the battery disconnected? What did it do when we jumped from the generator field to ground? Did we remove the regulator from the circuit?

Reply from Dick:

The regulator does not need to be polarized, only the generator. Make sure the shop knows the car is negative ground, there is a lot of confusion out there. The way to polarize the generator is to momentarily "spark" a hot wire from the battery to the armature terminal of the generator. This need only be done if the generator has been totally apart or may have gotten polarize backwards somehow. I suspect you real problem will turn out to be a poor contact in the armature circuit, either internally to the regulator, or in the wiring, even though you have checked for this. Sorry. You didn't say, but I assume the ammeter does show discharge OK when you turn on a load, like the lights? If not, it is possible that the ammeter shunt is incorrect or shorted out. When you short the field terminal to ground, you take all the regulation features of the regulator out of the picture, telling the generator to put out all the amps it can generate, regardless of other conditions. However, the current still has to have a path through the regulator cutout contacts and to the battery, via the ammeter, and this is where I suspect the problem will lurk.

Question from Bill (1959):

Tonight while driving home from work, I noticed my dash lights becoming very dim. I played around with the panel switch, and they got a little brighter, but still dimmer than usual. When I went to turn into my subdivision, I noticed the turn signal was not working, and that was my right one which is the one that stays on without having to hold the lever. I then noticed the gauge was showing that it was not charging, and the needle was all the way to D. I parked it, and disconnected the battery cable as I've gotten used to doing when I had a brake switch problem. I just had a new brake switch put in a couple of days ago, so that's been fine. Does this sound like a generator problem? and if so where is the best place to get one in Southern California? I printed out the page of resources from the club website, and see there's a very good one in San Diego, but is it best to have the old one rebuilt, or is there a new one which will fit?


From Dick:

The slow clicking turn signal is often the first thing one notices when the battery is not being charged.

NAPA stores stock the regulators, and they can send your existing generator out for rebuild, if you chose to go that way. You can also buy the needed parts from them and rebuild it yourself, which is what I do. Probably other stores can help you also; I happen to like the quality of NAPA parts and services.

From Greg:

Check the voltage regulator.

From John:

It could just as easily be the voltage regulator that's bad. I had one go out on my 60 on the way home from the WPC show in Vermont on the way home to RI at 11.00 at night.

Question from Steve (1959):

My car runs great, BUT, I had ignition problems last year and ended-up replacing the distributor.  I have also noticed that any battery installed begins to leak.  Do I just have a bad voltage regulator?  Or is the electronic ignition causing the regulator to fail. Again, this is not the electronic voltage regulator called for by Mopar, but rather the original type regulator. I do remember repeatedly "frying" the points with the old conventional distributor. Evidently, this also "fried" the pick-up coil and reluctor in the electronic distributor.

Reply from Dick:

If by leakage from the battery you mean out of the vent/fill caps, your generator is overcharging the battery, and this could be caused by either a bad regulator or a bad generator (grounded field). If it is leaking out of the case somewhere, you've got a mechanical interference at the battery holder, or severe vibration cracking the case. I cannot think of any connection between this situation and the electronic ignition, although I am aware that the Mopar conversion includes (or is it recommends?) you convert to an electronic regulator, which may not be available for your car. Frying points is usually the fault of an incorrect connection or a shorted out ballast resistor - your car should have a substitute for all this stuff, included with the electronic ignition kit. Pickup coils don't usually fail that way, they open up (resistance goes to infinity), so there may have been a coincidence, or something wired wrong somewhere.

Question from Joe (1959):

Ok, got the rebuilt generator back from napa on wednesday, five days when they said it'd only take half a day. It's dead today (Sunday). Story: engine was rebuilt, within a week, the generator died. My son drove the car for a week or two before getting the generator rebuilt. Put the rebuilt generator in, showed 16-17 volts when charging, now four days later it's dead again, when I disconnected the wires from it and let it run w. the engine, it's putting out 2 volts, no load. What ELSE could be wrong with the system to make the generator(s) go out like this? Since we had no problems with it BEFORE the engine was rebuilt, and presumably they disconnected all the wires and hooked them back up again, what else could short out the generator? Could the
regulator be screwed up? If the wires were improperly connected wouldn't something else go wrong, I mean, there's just a grd, field and armature wire to the regulator from the generator.


From Neil:

16-17 volts is too high, an alternator should charge at between 13.8 and 14.2 volts a generators output is normally lower with next to zero at idle.

Have all the ground straps been reconnected?

Check battery voltage then check batt pos to engine ground (anywhere on the block/head) the voltage should be the same if not it could be a grounding problem.

From Mikey:

Was the system polarized when it was put back together? Its always cheap insurance and a simple step to do. Presuming no crossed wires or damaged components, try that and double check the ground paths.

On low tension rings....its not a new phenomenon. Most of the hi-perf parts companies offer a low tension ring, as well as a narrower ring is available if you want to use a piston with correspondingly narrower ring grooves. Its pretty much for the guy who wants that last bit of horsepower, since ring friction is one of the main things that eat up power available. I'd take a set of moly coated standard tension rings, preferably the no-gap style thats available now, anytime. I suppose if I could see some actual independent data ( not from a ring manufacturer selling their own product ) on ring wear versus tension, I may give it a second thought.

From Steve:

If you were seeing 16 or 17 volts out of the generator there was something wrong. Did you replace the voltage regulator when the generator was rebuilt? I would suspect at this point you have cooked the rebuilt generator. It can not put out this voltage for long without overheating and

From Bill:

Put a nice new alternator on it, and save the generator for a time when the car is in pristine touring condition. Believe me you'll save yourself a lot of headaches, and your car will love you for it!

From John:

Your also supposed to polarize the generator by touching a wire from the batt. terminal on the regulator to another terminal.

From Roger:

I thought you polarized when you replaced a regulator. However, according to my trusty ol' MoToR'S Manual:

After the generator is installed, it must be polarized. Reconnect the leads to the regulator; then momentarily connect a jumper wire from the "Arm" to the "Bat" terminals of the regulator.

More questions from Joseph (1959):

A recap: son gets '59 engine rebuilt. A week later the generator goes out. Got a new battery, and the generator rebuilt. Put it in the Imperial, (polarized it), and five days later it goes out again. Measured the voltages when idling, got 16V eventually at the battery. High. Ok, put the rebuilt-rebuilt generator in last night, bought a new voltage regulator since I didn't want to deal with the other one. Same type of voltages. Starts out at 12V (what the battery was at), rising to 16V after five-ten minutes. The panel ammeter inside is full charge. Turn on the headlights, the voltage drops to 13.5V, the ammeter is showing charge, but only right of the middle line. (yes, polarized again, touched battery to armature at the regulator).

Does the voltage regulator only cut out on heavy load like headlights? I'm worried this 16V will do something to the generator again. But since there's really only the battery/regulator/generator in the charging system, what else would cause the 16V? I thought the battery was supposed to stop the voltage above 13.5V or so? Just don't want to burn the darn regulator again. Oh, I also ran a ground line from the battery directly to the regulator after I started up the car, just to make sure the generator ground (to frame and regulator), was all good.


From John:

The 16 volts won't hurt the generator but it is too high for the battery and unless corrected will shorten the battery's life. You will also tend to burn out light filaments quicker, but your headlights will be brighter. :)

First of all, check with another voltmeter to rule out a problem there, since you swapped regulators.

The regulator should be keeping system voltage at about 14.4 volts whenever the engine rpm is high enough that the generator is capable of providing the required electrical power. If speed is not high enough, you draw from the battery as indicated on your dashboard ammeter. The regulator also has a circuit to cut the electrical connection between the generator and the battery when the rpms are too low - otherwise, the battery would spin the generator like a motor, running the battery down in no time flat.

If your voltmeter checks out OK, it sounds like you need to adjust the voltage regulator so that system volttage is down around 14.4 volts.

From Dick:

I would add that the 16 volts might be caused by a discharged or high internal resistance battery. I'd watch the situation for a few hours of normal driving, to see if the voltage stabilizes at 14.5 or so. I' assuming here that this voltage is measured at the generator armature terminal. If you are measuring 16 volts right on the battery posts (not on the cable ends, on the posts themselves), you have either a sick battery or a hyper energetic alternator!

When you first installed this new system, if the battery was at only 12 volts even, it was partially discharged, so this may be normal operation temporarily, but make sure when everything stabilizes, that the battery voltage when not being charged is up to around 12.6 volts. If this is the case, I think you're OK.

The generator can easily put out even more than 16 volts if the regulator is calling for maximum charging. Normally this will only happen right after you start your engine or have otherwise severely discharged the battery. The wiring in the car has considerably voltage drop, so you won't see this voltage right at the battery post unless there is something wrong with the battery (very high internal resistance) or with the charging system. If the cause is in the charging system, the most likely fault is a ground on the field wire, either at the generator or at the regulator, and possibly inside either device.

Question from Bill (1959):

I brought my '59 Crown to my mechanic today to help me figure out where my electrical problem is coming from, since I tested both the generator, and regulator, and found they were both giving off a weak signal. My mechanic gave me several options, but suggested that I put in an alternator, which would be more reliable. He gave me several options, saying I could go with an alternator from a '63, or '64, whenever they started using them, or he could make a bracket and hang a new chromed Chevy alternator and regulator combined, with just one wire, and it was very powerful. He warned me that if I took that option, the Mopar Police would be all over me! I thought about the options, and came to the conclusion that I didn't really care what was charging my electrical system, as long as it was more reliable than what I had. I also told him that I was willing to update the mechanical, and electrical systems to make the car more reliable, as long as it has the original engine, body, and interior style. Please don't hate me, but after seeing that big chromed Chevy alternator, I told him go for it. I will of course keep the original generator, and regulator, and brackets, but may sell them if the alternator works out O.K. When I think deep down, I am really thinking of this car as more than just something to fix up, and take to shows, but more like a slightly less than everyday driver. I've even thought about buying two '59's, and driving the one that is running on any given day. The only thing stopping me is gas mileage, since I drive about 20 miles to work one way each day. I love my Imperial, and will do anything within my means to keep her on the road. Hopefully tomorrow I will get her back with her new shiny Chevy alternator. Don't hate me too much, it's a Chevy alternator, but made for Chevy pro stocks. I think the old lady will be very happy with it, after all, she deserves the latest technology!


From Dick:

It's your car, do what you want with it.

There was nothing wrong with the original design of your car's charging system - if it were repaired to it's like new state, it would serve you well for many years, just at it did when the car was new. In addition, it's parts were all simple and easily understood, and could be repaired by any competent mechanic from pieces on hand. You could drive it to southern Guatemala and the local "taller" could fix it for you - there are no transistors, diodes, slip rings or other tricky modern stuff in it.

The modern single wire alternator is indeed a vast improvement in performance and reliability, but when it fails, (and it will, some day) you are dead in the water until you find a replacement. The mechanic will not be able to look in a dusty old book to see what your car has installed - he will have to go by guess and by gosh, hoping to pick the right replacement part. My advice is to find out in excruciating detail exactly what vehicle this replacement charging system came on originally, and record for posterity the wiring changes made, and carry this information in the glove box for the day, perhaps 5 years down the road, when you will need it and not remember exactly what was done.

The hobby has all manner of participants. Some like to preserve original features, some like a modern reliability in an old looking car. Some feel a responsibility to maintain historically correct vehicles for later generations to wonder at.

The truly original examples of the older cars slowly disappear, as they are modernized with improved technology. Pretty soon, all we will have is old "looking" cars driving around with Honda running gear.

From John:

The generator that belongs on your car will do the job just fine if its working properly. A generator is a very simple device & you shouldn't have much trouble getting it fixed. Chrysler went to the alternator on the Imperial late in the 60 model year.

From Arran:

Whatever you do keep the original generator around in case you want to put the car back to original.  What Dick says is true, I believe that a lot of the problems encountered with these old cars electrically have more to do with an aged wiring harness then with the technology used. In fact you may find that the car still has a problem even with an alternator because of this. If I were going to go the alternator route I would find a MoPar unit similar to what the 1961 and later Imperials and Chryslers used on the 413 and 383 engines. At least in this case you use a factory looking bracket and a simpler bolt on conversion. Another advantage is that you can use a more factory type wiring scheme as opposed to a home brew one.

Question from Rob (1960):

My charging system went caput on me the other day. Even though the generator had been rebuilt last year, the drain on it probably caused it to fry a brush or two (the stereo, electric fuel pump and extra electric cooling fan created a much bigger drain than usual, and I can only assume tromped the brush).  Any ideas how to adapt the generator to work all my accessories?


From Steve:

Your generator was not made to handle the electrical "load" that is needed to run that electric fan. The stereo won't take much to run unless you have one of those huge boosters installed in the trunk. I put an electric fan in the '69 NY'er I had, and it used to put an enormous strain on the charging system which had an alternator. At night my lights would be very dim at idle when it thermostatically turned on AND while the fan was running. Things would return to normal once my engine revved up a bit, but the in-dash ammeter was sitting way to the right. I can only imagine what it would do to a generator equipped charging system. My alternator eventually fried....I bought another one and removed the elect-fan a few months later since I knew the new alt would turn to toast eventually too. A few years later I bought a '71 NY'er and installed the fan only to see my charging system straining once again. The fan was removed the next day. And sold for $20. That was $240 down the drain.

From Dick:

As for the generator problem, I see no reason that adding accessories to your car would cause rapid wear of the generator. The maximum charging rate is determined by the setting of the voltage regulator, and if all is correct, will be well below the point where the generator will be overstressed. The symptom of asking too much from a generator is thrown solder from the commutator bars (bright flecks of metal will be seen on the inside of the case radically outward from the location of the interface from the armature windings to the commutator). Rapid brush wear is more likely to be caused by an improperly assembled generator, or wrong springs, or wrong brushes, or bad bushings. If the generator is properly rebuilt, none of these things should be a concern. A generator in good shape should give at least 25,000 MI service before needing anything.

Follow-up from Rob:

My mechanics traced the current circuit from the generator through the light/dimmer switch, through the ammeter gauge, and back through to the battery, and found that the battery was losing 1 full volt. After replacing much of the wiring of the circuit, they got it down to an acceptable loss of 30% of one volt. So I should be OK for now, but shouldn't have all my various accessories on while idling, as my battery will drain like a tub.  My next task will be finding an alternator replacement with a higher amperage output.

Question from Dave (1960):

If the charging circuit is working correctly and you disconnect a battery lead with the engine running, should the engine cut out or still run? I am unsure that the circuit on our '60 is working correctly having just fitted a new armature and regulator box. Also in the 1960 manual it says "the generator should be polarized before it is operated as follows: make sure all connections between the generator and regulator and battery have been properly tightened then use a jumper wire to make a momentary connection between the battery terminal and the generator armature terminal". Does this mean the battery terminal on the regulator or the positive terminal on the battery itself, as I am unsure on this procedure. Can anybody help!


From John:

This is from the one on the regulator marked Bat to the one marked Arm. Just need to barely touch the terminal & it will make a spark. This is all it takes & the gauge should be showing some charge after doing this. If not, could be a problem with regulator or generator.

From Bill:

The car should run if the battery is out of the loop once started. As far as polarizing, I have done it at the generator, a momentary touch of the two terminals is all that is required. If it doesn't take try it again after two or three look for another problem. Does your amp gauge show a charge?




Question from Marc (1960):

I am still in the process of working all the bugs out of the car. When the car is running, I disconnect the positive terminal, and the car dies. Is this normal, the battery seems to die, Its not charging the battery, and the generator was just rebuilt.


From Dick:

This is not normal. Your battery is not being charged. You need to take the car to someone who will check out the charging system for you. Don't spend a nickel on the problem until you know what is wrong, as you may chase your tail all over the lot before you stumble on the real culprit. I believe most auto parts stores will diagnose the problem for you at no charge (pun intended).

From John:

Wouldn't the generator need to be polarized as it says to do when replacing the regulator?

Reply from Dick:

The rebuilder should have done this, but it wouldn't hurt to try. This is one of the list of things it "could be".

This page last updated August 22, 2004.  Send us your feedback, and come join the Imperial Mailing List - Online Car Club