'55 F-100, hot coil

Chuck (CA) · Apr 21, 2009

My friend has a nice 1955 Ford F100, 12 volt. Driving down the road it just stopped.
Towed it home and checked for spark.
No spark at distributor and coil gets HOT!

Any thoughts or suggestions? He's going to put an electronic ignition in, but wants to resolve this problem first.

Thanks,
Chuck

Greenday · Apr 21, 2009

Bad resistor

buickanddeere · Apr 21, 2009

What is the coils primary resistance? Lots of 6V coil"s have 12V marked on them because they are used on a 12V system with a ballast resistor.

Bob · Apr 21, 2009

The coil MAY have shorted or there may be a short in the primary wiring between the coil and the breaker points. (Or, even a shorted condensor.)

Check the voltage at the DISTRIBUTOR primary side of the coil... ignition "ON", points "OPEN", points "CLOSED".

Points "OPEN"... should have battery voltage.

Points "CLOSED"... should have near ZERO voltage.

If that checks out OK, the coil is probably bad.

You need to get the correct coil... if there is a ballast resistor ahead of the coil (could be a ceramic ballast resistor or a resistance wire between the ignition switch and the coil) you need a coil marked "USE WITH EXTERNAL RESISTOR".

If there's NO resistor ahead of the coil, get a TRUE 12-Volt coil such as a NAPA IC-14SB.

Kruse · Apr 21, 2009

How long has this been a 12V vehicle? A stock '55 Ford 1/2 ton is 6 volts. The F-100 went to 12V in '56.
So...has he been driving it this way for a long time or is this a recent conversion and you just realized the coil was hot?
This could determine if it was a failed component or the wrong parts were used for the 6V to 12V conversion.

Anonymous-0 · Apr 21, 2009

Put a 12v coil on the truck.It may have the stock 6v coil on it.

Oldmax · Apr 22, 2009

The 55 ford F-100 stock was 6 volt with pos. ground. so there could be a number of things wrong with it. would take back to the person that rewired for 12 volts and let them lick their calf over or start from scratch and go over whe system from top to bottom, Making sure wiring is correct like right polarity on coil if coil is resister type or not . They might have coil wired in reverse + to - & - to + .

barn E · Apr 22, 2009

How about solenoid sticking and continuously bypassing the resistance unit? If so wired. Dave

'55 F-100, hot coil

Chuck (CA)

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Greenday

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buickanddeere

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Bob

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Kruse

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Anonymous-0

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Oldmax

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barn E

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