6 volt to 12 volt conversion question

I have been working this winter upgrading some things on my 55 Royal Lancer in order to make it more drivable. This includes a ford 8.8, split brake system with adjustable proportioning valve, 4 wheel disc brakes, repairing some stress fractures in the frame around the steering box and fixing the transmission leaks.

I have been mulling over a 6 to 12 volt conversion for obvious reasons, but can't seem to wrap my head around a few things. Here is what I know and some questions.....

To the best of my knowledge all 6v automotive systems were positive ground, and all 12 volt are negative ground.

DC motors are polarity sensitive, meaning if you switch polarity they will turn backwards.

I believe (but could be wrong) that most automotive electric motors are internally grounded.

I have searched the net and found 12 to 6 volt step down transformers listed to run things like wipers, guages and blower fans after doing a conversion, but little to no information on switching polarity.

If I just rewire my car and switch to 12 volt neg ground, and use a step down transformer to run my wipers and blowers will they not turn backwards? Perhaps people just don't notice......the blower will still move air but much less effectively and the wipers may run, but will the park function work?

I have read and heard of lots of people running a 6 volt starter on 12.....everyone says it is great and turns over nice and fast......but again, switched polarity, won't it turn backwards? When I ask anyone who has done this if they changed to negative ground they say yes, then when I ask them about the starter running backwards I get a blank stare.

When people do 12 volt conversions do they stay with positive ground?

Won't the guages want to move backwards with switched polarity?

The light's are no problem, 12 v bulbs and some new wiring, relays for the headlights, horns are no prob, a 12 v relay and some 12 v horns. I will add a fuse box while I am at it (there are no fuses in 55, just one breaker.....scary). I would love to get rid of all the crappy cloth covered wire.....but don't want to have to re engineer the wipers, blowers and guages to use modern 12 v internals.

With 12 v I can run a modern ignition and alternator......both requiring negative ground.

Sorry for rambling, there must be some electrical gurus here or people who have done a conversion before that could point me in the right direction. Am I over thinking this?

Thanks!

I converted a 1955 Ford F100 from 6v pos. to 12v negative when I installed a 392 Chrysler FirePower Hemi from a New Yorker several years back. I didn't have to change any wiring because the 6 volt system ran a heavier gauge wire the the 12v. Just changed the light bulbs to 12v., took the voltage regulator from the Chrysler and ran a voltage drop to the gauges. Never a problem with the electrical system ever. A very easy conversion. This was back in 1972.

Actually all 6V were NOT positive ground, nor were all 12V neg. ground. I can never remember, but for a few years Chev and GMC pickups (6V) were OPPOSITE polarity ground.

And there has been some "heavy trucks" that were 12V pos ground. These used to be a real PITA for two-way radio shops, as some trucks had communications radios. Earlier (trunk mount) two way radios were often selectable for ground, but more modern transistorized radios required some sort of inverter. Expensive.

With that out of the way, MOST electric motors don't care as to polarity. Wipers, heaters, starters, as long as they are the old common "universal" motor that is "wound" field instead of more modern permanent magnet (mini starter) they will be fine, either polarity. IN FACT THEY WOULD operate on AC!!!! (Old 120V electric drills, vacuum cleaners, etc are essentially 120V versions of your heater motor. They would operate on 120V DC, either polarity and of course AC. This is why they were called "universal" motors.

So, what do you need?

Starter will be fine, and solenoid "might." If you can change the solenoid, I would

You will need 12V coil and matching resistor, or your choice of modern ignition

You will need "Runtz" instrument regulators for each electric gauge, such as fuel, temp, oil pres, etc, or build your own regulators, which you can do

If the ammeter is in good condition, you could use it. You will have to reverse the wire connections on the back for pos to neg.

You will need dropping resistors for wiper motors and heater blower, or change the motor.

Obviously change all the lamps

Obviously a 12V gen/ regulator or 12V alternator

I installed a one wire 12 volt GM alternator on my 6400 1953 Chevy holmes tow truck. It was 6 volt neg ground as all were from 47 on. All I changed was the coil and condencer, and light bulbs as they burned out. The beacon light never burned out . The heater fan worked better. the starter spun faster. Drove this truck this way for over 30 years. Never one problem. here is a picture from 2004.

They switched over to 12v in 56.
I parted out a 56 DeSoto and have some spare parts squirrel'd away
like the blower motor and possibly wipers we could compare. May work?

67Dart273 said:

Actually all 6V were NOT positive ground, nor were all 12V neg. ground. I can never remember, but for a few years Chev and GMC pickups (6V) were OPPOSITE polarity ground.

And there has been some "heavy trucks" that were 12V pos ground. These used to be a real PITA for two-way radio shops, as some trucks had communications radios. Earlier (trunk mount) two way radios were often selectable for ground, but more modern transistorized radios required some sort of inverter. Expensive.

With that out of the way, MOST electric motors don't care as to polarity. Wipers, heaters, starters, as long as they are the old common "universal" motor that is "wound" field instead of more modern permanent magnet (mini starter) they will be fine, either polarity. IN FACT THEY WOULD operate on AC!!!! (Old 120V electric drills, vacuum cleaners, etc are essentially 120V versions of your heater motor. They would operate on 120V DC, either polarity and of course AC. This is why they were called "universal" motors.

So, what do you need?

Starter will be fine, and solenoid "might." If you can change the solenoid, I would

You will need 12V coil and matching resistor, or your choice of modern ignition

You will need "Runtz" instrument regulators for each electric gauge, such as fuel, temp, oil pres, etc, or build your own regulators, which you can do

If the ammeter is in good condition, you could use it. You will have to reverse the wire connections on the back for pos to neg.

You will need dropping resistors for wiper motors and heater blower, or change the motor.

Obviously change all the lamps

Obviously a 12V gen/ regulator or 12V alternator

Click to expand...

Awesome information, thank you so much. That answers a lot of questions for me. Is see 12 volts and brighter lights in the future! You state that I need individual instrument regulators for each guage, can I not just power them all off a single 12 to 6 volt converter or dropping resistor such as the ones sold by Ron Francis, or do they need a better more controlled power supply?

Cheers

d55dave said:

Awesome information, thank you so much. That answers a lot of questions for me. Is see 12 volts and brighter lights in the future! You state that I need individual instrument regulators for each guage, can I not just power them all off a single 12 to 6 volt converter or dropping resistor such as the ones sold by Ron Francis, or do they need a better more controlled power supply?

Cheers

Click to expand...

You can power them all off one as long as it has a capable amount of amperage.
Which won't be much for powering gauges.

I have two voltage drop regulators in my current Dart.
One from 12v to 3.3 for powering all my dash LED's, and one 12v to 5 volt for powering and charging USB and 5v devices like phones, I pads, and tablet devices.

The 3.3 volt regulator is about 1 inch x 2 inch circuit board, and the 5 volt is about 2x2 with it's heatsink.
Point is, regulators don't need to be a huge device.

d55dave said:

Awesome information, thank you so much. That answers a lot of questions for me. Is see 12 volts and brighter lights in the future! You state that I need individual instrument regulators for each guage, can I not just power them all off a single 12 to 6 volt converter or dropping resistor such as the ones sold by Ron Francis, or do they need a better more controlled power supply?

Cheers

Click to expand...

Actually as TB said you may only need one. The key is amperage. "What do they draw?" Pay attention to the ratings if you go with the Runtz regulators.

For gauges you need regulators rather than resistors

Resistors are not a "one shot cures all" deal. Resistors are best used for non-critical devices, and they depend exclusively on the amperage drawn. If you read the destructions for the various "volt tap" devices made, they were kinda klugy and were used in different combinations for different loads.

If you can eliminate converters / resistors the better. That is why you change light bulbs and the coil, etc, to reduce the amount of dropping resistors, which do nothing but produce heat

Below is an example of "volt drop" automotive conversion resistors used for such things as wipers and blower. They are/ were sold by traditional automotive ignition lines, such as NAPA / Echlin, Standard Blue Streak and others

I converted a '55 Plymouth to 12v, but did it the easy way by buying a '56 parts car. Biggest pain to swap was the wiper motor.

I also have a few 12v parts that you can have for shipping cost. Some might be the same as Dodge.

ssba said:

They switched over to 12v in 56.
I parted out a 56 DeSoto and have some spare parts squirrel'd away
like the blower motor and possibly wipers we could compare. May work?

Click to expand...

Thanks for the offer, I am going to try and make my existing blower and wipers work, but I will let you know if I want to compare.

Cheers

GaryS said:

I converted a '55 Plymouth to 12v, but did it the easy way by buying a '56 parts car. Biggest pain to swap was the wiper motor.

I also have a few 12v parts that you can have for shipping cost. Some might be the same as Dodge.

Click to expand...

Same goes here, thanks for the offer, I am going to make my parts work first!