12 volt coil, 6 volt car?

H

hoof

Member
I am working on a '29 model a that my father bought. I have had it running, but never really well. The last time I was running it the ignition wire went up in smoke, literally. So I got all new ignition components, including a 6 volt coil. The car is still 6 volt positive ground. The coil in the car right now is very clearly marked 12 volt?
Am I wrong in assuming a car with a 6 volt battery will use a 6 volt coil?
Thanks,
CHAZ
 
Something I discovered a while ago, a friend was having trouble with his car. It kept burning out coils. I did some research to discover that the resistance in coils can vary greatly. This particular car was 12volt. He went to the local parts supplier and bought a replacement. That too burnt out.

It transpires that modern car with 12 volt electronic ignition use a 12 volt coil with a different resistance. If your older vehicle has contact points and you fit a coil suitable for electronic points the coil will burn out after a while. My friend went through eight coils before he found out. Most parts suppliers a quite happy to keep suppling the wrong parts (if they even know there is a difference).

Don't believe a parts man, check the resistance yourself before you buy your coil.
 
Look in one of the Les Andrews books. It has great detail about the correct coil. The local parts store could not supply what I wanted. Ordered it online. Cost about 30.00 for the correct one. Running improved a noticeable difference. Worth every penny.
 
Snyder's sells these:
 

Attachments

  • coil1.JPG
    coil1.JPG
    51.2 KB · Views: 85
  • coil.JPG
    coil.JPG
    28.7 KB · Views: 54
At your local parts store ask them what the resistance is on the coil they are trying to sell you. Then ask them to borrow their Ohm meter. All the time keeping your own meter in your pocket.
 
Coils are like mechanical gears, in fact the math behind gear ratios is the almost identical to turn ratios of transformers.
 
Still some electrical gremlins, but new coil and ignition wire and it is running like never before (since I got it).
CHAZ
 
Up until the advent of the HEI ignitions, so called 6 and 12 volt coils were actually 8-volt coils. In a 12-volt system, operation of the ignition is as follows:
>Ignition key @ START, 12 volts to the coil;
>Ignition key @ RUN, 8 volts to the coil via a dropping resistor.
 
You must log in or register to reply here.
Back
Top