Converting to 12v. Got a couple questions

[mike657894]

What steps do i need to take to change polarity? Do I need to change polarity. I want 12 volt because I want to put a radio in a hide away oak box with a couple reasonable speakers under the seats(6.5in). also I have two 12v tailights I have gm alternators sitting around and I have a 12v oogaa horn I fitted my old horn bell to. if my radiio is mounted in an insulator(wood box). i looked on the forum for good info but found alot of people saying why you dont need 12v so please none of that on this thread. Thank you for any info in advance. I have also bought a ballast resistor but i am not sure where to put it.

[mike657894]

im redoing all the wiring as a fire was avoided when the cotton roof batting was smoking from a short in the roof light. all the wires have bare spots from mice or time.

[Mike V. Florida]

What steps do i need to take to change polarity?

To change the polarity only, swap wires on Coil, ammeter, battery and use correct gen/alt.

To convert is another question.

This is from Ken at Kens Garage.


Battery

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.
Generator

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.
Starter

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

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.
Headlights

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.
Ignition

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
(619)460-3620
Horn

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
1-800-463-9275
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.

[mike657894]

thank you. that does sum up all of my questions.

[Chris in CT]

Hi Mike,

Two additional things you might wish to consider: One, it is probably worth it to convert the field coil on your starter to 12 volt. Most of the supply houses carry this conversion item. Two, you might want to install a 4 or 6 slot fuse block to the electrical system. When a short or electrical failure occurs, you will know in which circuit it has occurred, and the rest of the system will continue to operate while you attend to the problem in the target circuit.

I have done these on my own car and can attest to the efficacy of these additions. Happy Motoring!

[mike657894]

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Chris thank you. i am going to put on a fuse block.

[CarlG]

This is the fuse block I use:

[Dick Carne]

Hi Mike -
Another couple of thoughts for you to consider:
1. As Mike V. alluded, if you convert tot a 12 volt system, be sure to get a 12 volt coil with an internal resistor.
2. As far as a radio connection goes, we placed a small amp under the front seat of our Town Sedan, and I've been able to run an iPod through that as well as get Sirius radio. As far as the placement of the speakers goes, we used map pockets on the front cowl panels and placed speakers behind the flaps. When the radio is in use, we lift and secure the flap in an "up" position; when we stop, we'll lower the map pocket flap and all appears at least period correct. Good luck to you however you choose to proceed.
Dick

[mike657894]

I like the amp idea. its not too big in there and that would save on finding the space for the box

[dustyp489]

Mechanic Book 2 has the right info on this change , very easy to follow

[Binger]

This is great information. I have been considering running 12 volts on my coupe project. This is great information. I would have not thought of changing the amp meter. Thanks.