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1952 Chevy 6 V to 12 V Conversion (1949-1954)

Discussion in 'The Hokey Ass Message Board' started by HUSSEY, Apr 13, 2012.

    Joined: Feb 16, 2010
    Posts: 628


    I wanted to make a contribution and pass along what I learned when I converted my car from 6 V to 12 V.

    Before I get started I will say that I think this was a very worthwhile project for the money. Good charging and better reliability, great headlights, great starter cranking, and the ability to hook up a 12 V radio without putting a 12 V battery in the trunk. It is a bit involved but not very difficult, there's just a lot you have to consider. Just keep in mind that for resistive circuits when jumping from 6 V to 12 V, if your circuit resistance stays the same your amperage will double (Ohm's law: Voltage = Amperage × Resistance), therefore, you always have to consider how you're going to tame that 12 V.

    My first tip is to buy the 12 V conversion guide from the Fifth Avenue Garage:

    It's well written and easy to understand. He also has a lot of the parts you will need to complete your conversion. His parts are also available through Speedway Motors. I just happened to buy the parts from Speedway. They're out of Omaha and they can deliver to Kansas City overnight at a regular rate and I wanted to do this project over the upcoming weekend.

    The following are the items which will need to be addressed:
    1. Alternator
    2. Ignition coil
    3. Horn
    4. Blower motor
    5. Gauges
    6. Lights
    7. Turn Signal flasher
    8. Radio
    9. Cigarette Lighter
    10. Overview

    1. Alternator
    I selected a GM 10SI two wire alternator. These were common in 70s and some early 80s GM vehicles. The two wire alternator is externally excited so it will charge at low RPMs and does not rely on internal excitation such as a one wire alternator. I used an alternator for a 1980 Corvette which had the correct clocking. Delco Part No. 3342115. If you're paying more than $50 for the alternator you're paying too much, check your local parts store.

    Because my car had a 5/8 in. belt I had to get a 5/8 in. pulley. I picked this up from Speedway, Part No. 91016250. I believe 53 and 54 have a 3/4 in. belt.

    You can purchase an alternator bracket but it will run you 60-70 dollars. I made mine from my original bracket and an extra one I had. I flattened the upper bracket to fit.

    Figure 1: Original Alternator Brackets, One Hammered Flat

    Figure 2: Modified Lower Alternator Bracket

    Figure 3: Upper Alternator Bracket Hammered Flat to Fit

    Figure 4: Installed Alternator

    To wire the alternator you will need the DA plug from the Fifth Avenue Garage. His has, I believe, a diode in-line which allows you to shut off your car. I got mine from Speedway, Part No. 91064100. Without it, even when you shut of the key, power will be fed back through the excitation wire back through the ignition switch and to the ignition coil, keeping the coil energized, thus not allowing you to shut your car off. You could avoid the DA plug from the Fifth Avenue Garage by 1) Putting a switch in line for the excitation wire or 2) Putting in a new ignition switch which has an accessory terminal. The accessory terminal is isolated from the ignition coil therefore you won't get power fed back to the coil when the ignition is off. I chose the DA plug from the Fifth Avenue Garage because it's quick, easy, simple, and cost effective.

    To wire the alternator, plug in your DA connector and run the sense wire to the battery (or BATT terminal on the back of the alternator) and the excitation wire to the ignition switch. Connect the excitation wire to the terminal which receives power when the ignitions switch is in the run position. Next, hook up the original 10 gauge GEN wire from the voltage regulator to the BATT terminal of the alternator. At the voltage regulator splice together the 10 gauge GEN wire and the 10 gauge BATT wire. Remove and discard the 16 gauge FIELD wire which ran from the voltage regulator to the generator, you can also remove and discard of the voltage regulator. By doing these hook-ups you have hooked up the BATT wire on the back of the alternator which is routed through the ammeter gauge to the starter which is hooked to the battery.

    The Old Car Manual Project has original electrical diagrams:

    I've also made them available here:

    The following before and after diagrams should make this more clear:

    Figure 5: Before, Factory Charging System with 6 V Generator

    Figure 6: After, Modified Charging System with 12 V Alternator

    Figure 7: Installed and Wired Alternator

    Lastly was getting a new belt for the alternator. I had to make a couple of trips back and forth to the parts store. Luckily the guys at the parts counter were interested in what I was doing and were willing to accommodate me. The belt that fit was a Gates TR22425, 5/8 in. belt.

    2. Ignition Coil
    I opted to go ahead and upgrade my ignition system by installing a later model HEI distributor. I bought a distributor for a Chevy 250 on eBay for $65 and modified it to fit my 216. Same distributor out of a 1980 Chevy truck with a 250, one might be had at a junk yard but I didn't think $65 was too bad for a brand new one. You can find them modified to fit on eBay for around $125.

    Hooking it up couldn't be easier. Just re-use the power wire that went to the old coil. I think going with the HEI distributor is the way to go because you're going to have to buy an internally resisted 12 V coil anyways for a 12 v conversion.

    I did a write-up on the distributor, it can be found at:

    Figure 8: HEI Distributor Installed

    3. Horn
    You can swap your horns out for 12 V horns or wire your 6 V horns in series. By wiring them in series you in essence are applying 6 V to each of the horns. I wired mine in series and the install turned out really clean. I kept the power wire going to the driver's side horn and isolated it from ground. I drilled out the mounting bolt hole and inserted 1/2 inch plastic washers. I then used large rubber washers on the back and a couple of plastic washers on the front. This kept the mounting bolt and mounting surface from touching any of the horns mounting surface. I then spliced the power wire for the passenger’s side horn and attached it to the mounting surface of the driver's side horn. They're now wired in series.

    I've also been told to swapped out the 6 V horn relay with a 12 V horn relay. You can get this off the shelf at an auto parts store.

    Figure 9: Horn with Insulators Installed

    Figure 10: Horn Installed with Horns Wired in Series

    4. Blower Motor
    For the blower motor I wired a resistor in series which can be had from the Fifth Avenue Garage or Speedway, Part No. 91064103. The instructions advise that you install it in an air flow path to cool it. I installed it across one of the heater duct floor outlets. I've been told you can also source a 12 V blower motor from a later model Chevy.

    Figure 11: Miscellaneous Parts, Runtz Voltage Reducer, Blower Motor Resistor

    Figure 12: Installed Blower Motor Resistor

    5. Gauges
    The only gauge which is affected is the fuel gauge. Fortunately it has an ammeter gauge in lieu of a voltage gauge and the temperature and oil pressure gauges are mechanical. To reduce the voltage of the fuel gauge you need to use a voltage reducer, different from a resistor. I used a Runtz voltage reducer available from Fifth Avenue Garage or Speedway, Part No. 91064101. There's a how to in the tech archive on the HAMB on how to make these, search for "How to Build a Voltage Regulator for"; or use the following link:

    The Runtz are $18 a piece when bought assembled so if you needed them for several gauges there would be a cost advantage to making your own but only needing one I decided to just buy one. The Runtz can be seen in previous Figure 10 and installed in Figure 11.

    Figure 13: Installed Runtz on Fuel Gauge

    6. Lights
    Lights are simple but will end up nickel and dimming you to death. The following is a list of all the bulbs/Part No. that I had to replace. I would suggest the Sylvania Silver-star for the headlights. They're bright and give off a clean white light.

    Headlight H6024ST (2)
    Front Park and Turn Signals 1157A (2)
    Rear Park/Brake/Turn Signals 1157 (2)
    Back-up Lights &#8211 1156 (2)
    Gauges 57 (4)
    High Beam Indicator 53 (1)
    Turn Signal Indicator 53 (1)
    Ignition Switch 51 or 57 (1)
    Clock 67 (1)
    Dome (1)

    7. Turn Signal Flasher
    Just replace your existing 6 V flasher with a 12 V flasher. This is an off the shelf item at the parts store.

    8. Radio
    Mine didn't have an original radio in it when I bought it. For factory 6 V radios, I have been told that you can't use a resistor on them like the blower motor; they just draw too much power. I believe you can have these converted to 12 V but it's expensive.

    I mounted a Radio under the dash with 6x9 speakers in the rear deck.

    Figure 14: Radio

    Figure 15: Speakers

    9. Cigarette Lighter
    Just replace with a 12 V one. I'm going to try and swap the knobs so I can keep my original ivory type knob.

    10. Overview
    You could do this job in smaller chunks but make sure you have the voltage reducer on your fuel gauge before you hook up 12 V or you run the risk of burning it out.

    As far as the starter, I've been told you don't have to do anything to them. The starter will crank faster with 12 V applied to it. I was a little concerned that it would heat up and get burnt out with the higher voltage though I've been told that it will be fine. You're cranking the starter for only a short period of time.

    The following table summarizes all my parts and part costs. Probably a bit higher than what you would gut all the parts start totally up really fast. A big chunk was all the bulbs, $95, I probably could have done better on these. In my opinion, it was well worth the money.

    Table 1: 12 V Conversation Cost Table

    The above excludes the cost for the radio, distributor, and 12 V battery.

    If I've missed anything please feel free to add.

    If you want an easy to print PDF copy of this write-up you can get one here:

    Last edited: Jan 3, 2016
    AHotRod likes this.
  2. Big T
    Joined: Aug 29, 2006
    Posts: 638

    Big T
    from Florida

    Nice job, pics and summary.
  3. biscaynes
    Joined: Mar 16, 2008
    Posts: 1,648


    Great thread! :)
  4. gwarren007
    Joined: Apr 3, 2010
    Posts: 381


  5. Nice write-up and summary of what is needed. To save a bit of money, instead of the Runtz reducer for your gages, use a "7806" integrated circuit type voltage regulator. The 7806 is about $1-2, and handles up to 35 volt input and controls down to 6 volt output at 1 amp capacity. Very easy to hook up using a metal piece for a heat sink. Works great for gages, not for blower motor or wiper motor.

    I have this setup on my 37 Chevy and the gas gage works great.
    jakespeed63 likes this.
  6. Vimtage Iron
    Joined: Feb 28, 2010
    Posts: 536

    Vimtage Iron

    Do these 12 to 6 drops work better than the old ceramic volt a drop, I'm using one for clock and gauges and the gas gauge is always moving around and jerkey and the temp goes off on its own now and then.
  7. nice write-up, I'm sure it'll help some people out
    Toqwik likes this.
  8. old soul
    Joined: Jan 15, 2011
    Posts: 1,094

    old soul
    from oswego NY

  9. Commish
    Joined: Jan 9, 2010
    Posts: 379

    from NW Ok

    Good write up, clear and concise, well drawn diagrams. I only have 2 nits to pick with it. The way you wired the heavy battery wire through the ignition switch is going to put all charging load on the switch contacts. It should be wired in a direct path from the alternator back to + post of battery, or where the battery cable terminate at the starter, it will be hot all time. The other thing is the sense wire, although it will likely work that way, it is better to have it out in the system somewhere in a more remote location from the alternator. It will sense total loads on the whole system better that way.

    Edit: Just went back and looked at your diagram and realized the heavy wire might not be switched. If you just have it connecting to the wire coming back out to the battery on the same post, then that is basically what I was recommending, although I still like the heavy wire unbroken from Alt. to Bat., running through the amp gauge is fine.
    Last edited: Apr 14, 2012
    jakespeed63 likes this.
  10. That's great! SAVED!! Thanks!

    Last edited: Apr 14, 2012
  11. Thanks for the info, good descriptions.
  12. 52Poncho
    Joined: Apr 23, 2011
    Posts: 256


    Thanks for the PDF I'll use it on my Poncho.:)
  13. RagtopBuick66
    Joined: Dec 12, 2011
    Posts: 1,182


    AWESOME write-up. I personally appreciate this, as I've been considering the 6V to 12V conversion on a 53 210 I just picked up. I'll get it running on 6V and start putting together my shopping list to convert to 12V, and buy it item at a time to be installed as soon as I've got everything in one box. Thank you!
  14. spiffy1937
    Joined: Apr 9, 2006
    Posts: 729

    from Florida

    Thanks for posting this info. I am going to be doing this soon on our '50 Fleetline. :)
  15. rusty but trusty
    Joined: Mar 7, 2012
    Posts: 5

    rusty but trusty

    Thanks for the info i am cosidering doing this on my 53.
  16. HUSSEY
    Joined: Feb 16, 2010
    Posts: 628


    As your edit says, the wires are just gathered on the same terminal of the ignition switch. I don't disagree with the sense wire. The voltage will be strongest comming right out of alternator and drop back to the battery. There's an arguement if the way I did it was correct then why wouldnt they just hook it up internally to the alternator. I may run a jumper from the sense wire over to the battery and see how it changes the output. I'm going to suspect thought that it doesn't make a very big differance given that the electrical loads of the car are pretty small.

    Glad my post could help a few folks out, I know I've learned alot from the information available here on the HAMB.
    jakespeed63 likes this.
    Joined: Sep 16, 2010
    Posts: 612


    thanks for the info
  18. HUSSEY
    Joined: Feb 16, 2010
    Posts: 628


    With a ceramic resistor, the voltage drop across it will change with change in current flow.

    Ohm's Law -- Voltage = Amps x Resistance
    Kirchoffs Law -- Sum of the voltage drops in a circuit equals the source voltage

    A fuel gauge sending unit is basically a potentiometer. When the level in the fuel tank changes the resistance of the sending unit changes, which in turn changes the position on the fuel gauge. As the resistance of the sending unit changes so does it's voltage drop which affects the voltage drop across a ceramic resistor.

    What you need is a constant voltage source, which is what a voltage reducer provides.

    Though I'm not an expert, I'd be willing to bet if you changed out your resistors to voltage regulators that would correct your problem
    jakespeed63 likes this.
  19. nek635
    Joined: Oct 9, 2010
    Posts: 27


    awesome job, publish a book "12volt for DUMMIES"
  20. Trichop
    Joined: Jan 8, 2008
    Posts: 219

    from Eaton,Ohio

    Great article!
    I'm trying to remember back in the mid 80's when I did my 1948 Chevy coupe 6 to 12 volt conversion
    If I remember right, you can use the pulley off the generator and install it on the alternator....tha shaft size was the same
    I did have to use a thin washer under the pulley so it didn't rub the alt case

    I sold the car at the "Frog Follies" to a young guy from Indiana (Ft Wayne?)
    His Dad bought it for him as his first car (Dad had a 33=34 Mopar sedan)
    It was Bright Yellow
    I often wondered if the Kid is on here
    jakespeed63 likes this.
  21. Sin7
    Joined: Oct 5, 2011
    Posts: 99

    from Wylie TX

    Whoa! This is perfect man. Thanks!
  22. Dads1954
    Joined: Dec 24, 2008
    Posts: 28

    from New York

    what a great thread. thank you for the information. you have saved many asprin cause i know this would have been a headache to figure out.

    great thread.
  23. RawDeal
    Joined: Nov 29, 2002
    Posts: 156


    I just want to thank you for this great thread!

    top info!!! Thanx!!!
  24. Terrible Tom
    Joined: Feb 15, 2010
    Posts: 573

    Terrible Tom

    Nicely done. I'm saving it for a reference if I have to do the conversion in the future. Thanks!
  25. pq55
    Joined: Jul 5, 2005
    Posts: 89


    Make the task a lot easier for the 49, i'm doing right now. Thanks for the good work.

    The #51 bulb is 6v use #1893 instead.

  26. HUSSEY
    Joined: Feb 16, 2010
    Posts: 628


    Good catch, I'll have to get that corrected. I must of wrote down the 6V number instead of the 12V cross referance number because now that I think about it my turn signal flash indicator is a bit bright.
  27. d2_willys
    Joined: Sep 8, 2007
    Posts: 4,103

    from Kansas

    Two things:

    1. A #53 will replace a #51 bulb
    2. You may have issues with standard 3 pin flasher (550). Examine the wiring diagram and you will see that the dash indicators return through the opposite side front turn signal. If you use a 550 flasher, your dash indicators will both come on when in left or right turn switch positions. The outside lamps work just fine. PM me if you need a remedy that uses the popular 550 flasher.
  28. I was reluctant to convert to 12V but after I did it turned out to be one of my best modifications. Headlights are much better and its nice to not be limited when it comes to radios, radar detectors, tachs, etc...
  29. Rusty Heaps
    Joined: May 19, 2011
    Posts: 607

    Rusty Heaps

    I'll tag this one for future reference, thanks
  30. Hugh in NC
    Joined: Jan 14, 2012
    Posts: 11

    Hugh in NC

    I just finished this same conversion on my '51 Styleline Deluxe. The only difference was that I converted the rear stop/brake lights to LEDs and added a third brake light in the rear window. You can't be too safe these days, who knows what will be coming up behind you. Anyone that follows your instructions will have a successful conversion.


    Last edited: Sep 14, 2012
    jakespeed63 and 19blockhead72 like this.

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