The old coil is shot. Do I replace it with one that says: "12 volt - use with external resistor"?

Thanks y'all.

Todd

'75 was about the time of the transition from points and a condenser, to the GM HEI (High Energy Ignition) system. Which do you have? It might be a good time to go HEI if you don't have that already.
Matt

It's the points and condensor version. Oh, I forgot to mention that the old (looked to be original coil and measured nothing on ohm meter) coil was deteriorated on the sides and there's no way of telling what it ever said. Thus my question. I'm looking to buy this RV, but I've kindof volunteered to try to get it started and don't want to spend much money on it. The fellow has a couple of old coils, but they all say that they are for external resistors or resistor wire.

Thanks much!!

Todd

To get it started it doesn't matter. If it needs an external resistor the voltage will be higher to the points, no big deal for the first 1000 miles or more.

Most 12 volt coils are not really 12 volts. They are 8 volts or so, with a dropping resistor or resistance wire used to lower the voltage when the coil load is on the circuit.

Engines usually benefit from a hotter spark when starting, so the starter solenoid provides a terminal to bypass the resistor or resistance wire and provide a full 12 volts to the coil for the time the starter is engaged. This extra hot spark is a little hard on the points, but it makes little difference for the short time it is used. If the solenoid has two small wires on separate terminals, the vehicle is wired for a resistor or resistance wire. One is hot from the starter switch and the other is hot going directly to the coil, bypassing the resistor. The studs on the solenoid are 10 32 and 8 32, with the wire terminals matched, so you get some help in reconnecting if they are removed from the studs.

Does the coach have the Barth build tag? The numbers might help Nick use his secret decoder ring to tell you for sure which coil is which.

I will agree with BBM on the desirability of HEI, but, in your situation, it looks like coil is the way to go. How do his other coils test?