6 volt ignition coil

[Summershandy]

Got a bit a brain fart. Went down to my local NAPA to check on ignition coils for my '54 Pontiac and the counter person asked, "do you have a resistor?"

The NAPA coil is printed NO EXTERNAL RESISTOR REQUIRED. So I searched and found:

 

General Motors vehicles used the same 6-volt non-resistor ignition coil from 1923-’54. When they converted to 12-volt in 1955, the coils were 12-volt and externally resisted.

 

So I'm assuming their coil is fine?

 

[The 55er]

What's wrong with the coil that's in your car now? Does the car start and run OK?

[Guest]

52 minutes ago, Summershandy said:

So I'm assuming their coil is fine?

Yes.  The only reason for a resistor is on 12 volt cars is to cut the voltage down so the points don't burn.  When the ignition switch is turned to start, the resistor is bypassed to give a hotter spark, when it springs back to run the resistor is in the circuit.

[Summershandy]

24 minutes ago, The 55er said:

What's wrong with the coil that's in your car now? Does the car start and run OK?

 

Well, ya but I don't know how old it is. I changed most everything electrically and never did change it out. Not sure why I didn't. 

I still want to check the spark and reinspect the points before summer. New coil was just a thought and didn't know about resistors. 

[Bloo]

If it works ok I wouldn't worry about it.

 

Also, there are 6 volt coils that use a resistor, but no normal shaped ones that would bolt on a Pontiac and fit right, at least none I know of, and I have looked.

 

1 hour ago, Summershandy said:

The NAPA coil is printed NO EXTERNAL RESISTOR REQUIRED. So I searched and found: General Motors vehicles used the same 6-volt non-resistor ignition coil from 1923-’54. When they converted to 12-volt in 1955, the coils were 12-volt and externally resisted.

 

That ain't right. Cadillacs were positive ground through the mid 30s or so, unlike most other GM cars. Those Cadillacs had different coils listed for positive ground. Also there were "electrolocks" on some or maybe all GM cars in the 30s. There were multiple types of coil for multiple types of electrolock.

 

Assuming your Pontiac has a normal looking coil with a tower and 2 small terminals next to it (I think so), the NAPA coil should be the right one.

 

 

Edited March 3, 2020 by Bloo (see edit history)

[Frank DuVal]

Regular looking ignition coils with the center tower and two small terminals do not care if positive or negative ground vehicle. Just connect the + and - terminals correctly!  GM usually did not use Ignition and Points as terminal indicators. If it is I and P (or D for distributor), then you would need to know what the manufacturer had in mind for polarity. I have only seen this nomenclature on 12 volt coils, typically Ford. 

 

Cadillac was positive ground up into the early 50s.

 

 

[The 55er]

Sorry, but Cadillac was not positive ground into the early 50s. This info says 1946 and up Cadillacs were all negative ground. I remember working on a 1950 Cadillac and it wasn't positive ground. I also have a wiring diagram that clearly shows 1940 Cadillacs were positive ground so it must have changed sometime between 1940 & 1946. 

[Grimy]

1 hour ago, The 55er said:

Sorry, but Cadillac was not positive ground into the early 50s. This info says 1946 and up Cadillacs were all negative ground. I remember working on a 1950 Cadillac and it wasn't positive ground. I also have a wiring diagram that clearly shows 1940 Cadillacs were positive ground so it must have changed sometime between 1940 & 1946. 

Cads through 1942 were positive ground.  The 1946 and newer models were negative ground. IDK about any production during the war, but believe they were probably held-over 1942s and thus positive ground.

[Frank DuVal]

Yep, misstyped, should have been early 40s.....😪

[Summershandy]

Took the coil out tonight. Umm ya, not good. Poor thing. I also forgot one of the terminals were stripped from someone before me. I'll just pick up another.

 

 

[Bloo]

Check your coil wire! It might have just got wet, but a bad wire can do that too.

[Summershandy]

When I replaced the wires couple years ago, I don't remember the coil looking like this. It wouldn't be me not to check or clean it before replacing the wires. I've only driven the car once in the rain and that was when we were leaving a show and got caught in it. I can't imagine the coil getting wet. This one shocked me. I had to make the wires and was the first time I've done so. The coil wire looks ok but I'm going to check how well it connects to the coil. I could always make another, it's only about 10" long and I have left over wire.

The engine started and ran quite well except for the odd hesitation off start and sometimes a light jerk after a long drive at cruising speed. It'll be interesting to see if Mr coil had any part in it.