How To Convert Your 6-Volt System to a 12-Volt System


Imperial Home Page -> Repair -> Electrical System -> Battery ->Converting 12-volt to 6-volt

The How- To's on How To Convert:

This information is specifically for the 1955 conversion, but maybe you can also gain some knowledge from it if you would like to convert an earlier model...

I like my cars to be original, but using a 6-volt positive ground system is just too much trouble. My cars are toys I use and enjoy. If I was restoring museum pieces that just had to look good, I guess I'd retain the 6-volt system in the '55's. Some of the big benefits to me in having the 12-volt negative ground system are that the engines start quick (I leave in the 6-volt starter), 12-volt light bulbs are easier to get, and my cell phone plugs into the cigar lighter.

Fortunately, the '56 is the mechanical twin of the '55. So every 6-volt electrical part in the '55 has a corresponding 12-volt part in the '56 that will bolt right up. The necessary parts can be gotten from '56 parts cars, or just by ordering the piece intended for the '56.  Andy Bernbaum is a great source for many of these pieces.

Another option is to switch to a 6-volt positive ground alternator:

This information came from the following question by Jim:

I have purchased a 6V pos. ground alternator (48/50 amp out put) but am unsure as to how to integrate it into my system. It is a one wire out let Alt. My question is "what do to do with the battery field. & arm connections on the regulator so the system will operate through my dash ammeter?" The regulator will no longer be a part of the system. Any and all suggestions appreciated.  

Reply from Dick:

First thing would be to discard everything remaining of the original generator and regulator wiring, and connect the one wire from the new alternator to the end of the wire that came from the old regulator terminal through the firewall to the ammeter. This will be a very heavy wire, probably a #10, most likely the largest wire that goes through the firewall.

You are aware, I suppose, that there are Autolite generators that will supply your load. The senior Packards of the late 40's use an Autolite generator which provides up to 45 Amps. My 47 Limousine has such a generator, and I also have many extra drains on the system, and the generator keeps up with everything at any speed above 30 MPH. This includes 4 heaters, a humungous 8 tube radio front and rear, Sealed beam headlights, Trippe lights, 4 tail light bulbs, electric wipers, overdrive, reading lights in the rear compartment, etc etc. Admittedly, in bad weather, when everything is on and I have to sit at traffic lights idling, I see some pretty horrendous discharging on the gauge, but with a good battery, it comes back in a few minutes of freeway driving. The Packard ambulances, by the way, had an even bigger generator, but this is hard to find. The big generators are pretty beefy, and take a 1" wide belt to drive them, which may prevent your adapting one to your car. If you want to pursue this, I can look up the generator number for you, and maybe even steer you to a potential source for one, and the regulator which goes with it.

Reply from Bill:

Just replace the generator with it and hook the wire to the battery.  

Follow-up from Dick:

He said he wanted the ammeter to function, that is why I suggested he hook it up to the old current feed through the firewall. Your method would also work, and is easier, but it would not show the charging current, only discharges, and that might make him concerned as to whether or not the alternator was doing its job.

And Still Another Option:

I have installed a powerful 12 volt stereo and CD changer for my daughter in her 1954 Imperial.  I had to buy two (2) inverters that converted the 6 volt to 12 volts.  The first inverter is connected to ignition key power source (the original power source for the six volt radio).  And, for the purists, I did not "cut" the dash.  I hung the new radio below the dash--tons of room.  The CD changer is in the glove compartment.  I ran the second inverter off the power source next to the battery in the engine compartment.  This power source is used to run the "memory" in the radio including the clock and radio settings.


How can I make my 6-volt system work better…I would like to keep it.  (Problem is the generator is not charging the battery.  But none with a 6 -volt generator.  The main reason I was considering going to a 12-volt system is that my wife would like to have a nice stereo in it ( and trouble shooting tips for the generator.)


From Bill:

One other thing is you can if you are looking for a more reliable system keep the 6-volt but use the one wire alternators that are available. About  $100.00, no major modifications and easily put back to generator.

  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 commuator 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 overoil 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 or 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.   If you need more detailed help, e-mail me and I will try to be more specific.  On the stereo, there are two ways to go.  One is a converter, which is available from various sources.  It takes your 6V positive ground and converts it to 12 volt negative ground.   The other solution, and the one I prefer for my 6 volt cars, is to go to Radio Shack and buy their 12 volt gel cell battery.  It will run a CB or radio for weeks without recharging.  A tape or CD player draws more current, and might be too much for practical use of the separate battery.  You can figure it by noting the current label on the device, and comparing it with the Ampere-Hour label on the battery.  If your radio draws 0.1 amps, and you buy a 10 AH battery, it will run for about 50 hours use before you have to recharge it.  Just divide the AH rating of the battery by the amps of the load, and allow about a 50% discharge, and you can figure any battery life.

Question from Xavier (1955):

I just purchased my '55 Imperial and had some questions.  Are there any kits available to change it to a 12V system and keep my power steering/windows/seats (power steering pump is located on the rear of the generator)? 


From Mark:

The only "kits" I know of to change a '55 Imperial's 6 volt electrical system to 12 volts are those very rare "For Sale: 1956 Imperial, rusted parts car" ads that appear from time to time. If you're lucky enough to find one, they would have all the parts you need, including the Gemmer Hydraguide power steering pump/generator.  

But I have to ask: How bad are your electrics if you must change them all out? Are they really that fried? The one time I did a 6- to 12-volt conversion I came away convinced that the result was DEFINITELY NOT worth the effort. (And that was on a relatively electrically simple Dodge!) All that time and money would have been much better spent elsewhere. There's nothing wrong with a well-maintained 6-volt system. A '56 12-volt car starts marginally easier than it's one-year-older brother. The only possible advantage to 12-volt electrics is that you can install any sort of audio system you may want. (And there are ways to accomplish that in a 6-volt car, if need be.) In short, unless you need to replace 'most everything for your 6-volt car, save yourself all the headache and don't bother with the conversion. And so say I!

From Ben:

I agree with Mark on leave the 6 volt system alone, I was going to attempt it on a 47' Che*y I had and quickly changed my mind after I found out how much it cost (let alone how long it would take me)! I found a 6-volt timing light and a 6-volt battery charger and a hand full of resistors were a lot easier and cheaper.

From Larry:

The C-70 models (limo and 8 passenger sedan) had 12-volt systems so you could use the generator and other components from a C-70 to convert. You could also use the generator from a '56, though the polarity is reversed, there is a way (supposedly simple) to change it. My '55 C-69 had the 12 volt system when I bought it in '76; it appears to be factory installed, not retrofit. Every electrical part in the car matches part numbers with the C-70. My dad used to work for Chrysler, at two different assembly plants, and said they sometimes would run out of parts and rather than stop the line, would build with what they had. That was his explanation for my '55 having 12 volt electricals.

Question from Drex:

 I'm sure this topic has been discussed before I joined the club, but would somebody fill me in. I just received a new catalog of vintage parts to drool over and as I making my wish list out, I came across the battery that advertises itself as a "6-12" volt battery. The caption reads,"delivers 12 volts for starting, then switches back to 6 volts for regular electrical operation. Requires no modification to the car." Do these things work and are they worth the money? Furthermore, I'm afraid it will fry all my 6 volt electric. I know a few of you experts may have knowledge on this. Please enlighten me before I spend $185.00 I'll regret 50 times more.


From Dick:

I beg you, don't do it! If you are having problems with your 6 volt system, lets discuss that and fix them. Changing to a higher voltage is, to my mind, putting a band-aid on a cancer. It only delays the time when you have to deal with whatever has deteriorated (you know the car was reliable when it was new), and very likely will cause early failure of other parts of the car, some of which may well be nearly irreplaceable. This is my opinion, you will receive others I'm sure, but take it from one who still drives 3 different cars frequently that are still on 6 volt systems, all luxury cars, all with very large hard to crank engines, and I have never had a starting or cranking problem I could not fix by just going back to basics - getting the right parts, and installing them right!

From Ken:

I agree with Dick.  If the six volt system is set up properly, it will be very satisfactory. Also, be sure the engine is in a good state of tune, timing, carburetor, etc.   My '48 and '49 Dodges are both good starters, and the '49 (1-ton truck) has especially bright lights.

From 4-toes:

A few thoughts about 6v / 12v systems in cars. Six volt systems worked fine for years. If the electrical components are in proper condition all should work well. Twelve volt starters, accessory motors, etc. do not provide any more power than their equivalent 6v counterparts. They do draw more amperage to get the same power. So if the battery is bad, or connections corroded, bad bearings etc. it is more of a problem because of the higher current. 

The change to 12-volt improved some reliability but the primary reason was to save production costs. The lower amperage allowed smaller batteries. It also allowed smaller wires and cables. Compare the size of the starter wires for a 6v verses a 12 v system. Multiply the savings in just the cost of the copper times the numbers of cars produced and you can imagine the savings. Twelve volts allowed smaller, less expensive, components, smaller wires, and, initially, an advertising advantage. "NOW WITH 12 VOLT SYSTEMS" Then consider such things as reduced labor in handling and installation, smaller screws and connectors, reduced storage space for parts and raw materials, shipping weight costs, etc. With more accessories and lights becoming more common there also was a growth in operating current requirements. Going to 12v also helped to offset the need for even bigger wiring. It just keeps adding up. Considering the numbers of cars involved, a $5 saving per car is a big deal.

Question from Jeff:

 I recently purchased a 54 New Yorker. The previous owner had no clue of 50's electronics, so he stuck in a 12-volt battery with negative ground. (Is that right?) It started and ran great but it would not charge. So I stuck in the correct type 6-volt positive ground battery. It starts and runs fine but I have not checked whether it charges or not but should I polarize the voltage regulator? Any other ideas or things I should watch for?  

Reply from Dick:

There would very likely be some damage to the gauges and bulbs. If they are all working OK, then the 12-volt battery must not have been used for more than a few minutes that way. If the gauges are acting up, we will have to table that for now, you might have zapped the gauge regulator (yes, 6 volt car have them too) or one of more of the senders. I hope no one turned the radio on!  If the car is not charging, it is related to the 12-volts, not the negative ground. 

The only thing reversing the ground would do is 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. 

Fortunately on these cars it is very easy. I don't know for sure that your car has an ammeter, but the following assumes that it does. 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 aren'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.

This page last updated September 1, 2001.  Send us your feedback, and come join the Imperial Mailing List - Online Car Club