12 Volt Conversion


Golfing Buddy

How I Converted My Model A to 12 Volts

This web page is to pass on to you how I converted my 1931 Victoria to a 12 Volt negative ground system. I don't pretend to be an expert nor imply that mine is the only way to go. I do hope that my experience may be of value if you decide to convert your car.


Any good 12 Volt battery will do as long as it will fit your battery box and hold down. I selected a 72 month, 675 cranking amp, universal battery.


I installed a GM 63 Amp Alternator with an internal self exciting voltage regulator. The hook up is one wire, the same as the existing generator. You will need to make two small brackets to mount the alternator or you can use two shackle bars and drill out for the proper size bolts.

An alternator pulley can be purchased from your friendly Model A parts supplier.


No modifications are necessary to the starter. Just touch the pedal and enjoy really fast starts.


I changed the standard 20 amp ammeter to a 30 amp ammeter as an alternator will peg the standard meter. You must reverse the leads on the ammeter due to the change in polarity of the battery.

Your neighborhood Model A parts supplier carries the 30 amp ammeter.


Since I installed an alternator I opted to go all the way for headlights and convert to Halogen bulbs. The conversion is relatively easy. You can purchase a kit to modify your existing reflectors or you can purchase new reflectors with the Halogen sockets installed. You must install an alternator to successfully operate Halogen bulbs.

6 Volt kits are available.

What a pleasure to be able to really see while driving at night.


You could install a 12 volt coil and a resistor to reduce the voltage to the points.

I elected to install a PerTronix IGNITOR electronic ignition system. This is an extremely easy system to install as it fits entirely inside the distributor; no outside boxes are required. Kits are available for the standard Model A or B, early V8, and Mallory distributors. Both 6 and 12 kits are available.

Kits are furnished with a new coil as the correct coil resistance is very important for proper operation. Kits are distributed by:

Remund Ignitions, Inc.
P.O. Box 857
Lemon Grove, CA 91946-0857


Getting the horn to work properly was the most perplexing part of the conversion. I tried several "voltage reducers" from the local parts stores but none could handle the current demands of the Model A horn. I finally purchased a 0 to 2 Ohm variable power resistor with a 100 watt rating from an electronics supply house. I selected a variable resistor in order to optimize the voltage to the horn.

The resistor I purchased was am Ohmite D100K2RO ($15.87) with two Type 12 brackets ($0.55 ea.) (Newark stock nos. 13F671 & (2) 13F099) from:

Newark Electronics

Branch offices of Newark are located throughout the United States. Minimum order is $25.00.

An alternate approach would be to puchase a 12 volt horn.

Light Bulbs

The following bulbs can be used with a 12 volt system:

Cowl, Tail, and Dash Lights - #89, 6 cp
Dome Light - #67/97, 4 cp
Stop Lights - #1156/10, 32 cp

Turn Signals

If you have a Signal-Stat turn signal it will be necessary to change the flasher to a Signal-Stat #180 and the bulb to a #1445.

Click to return to, Miss Vicky Send Ken E-Mail

Return to Ken's Home