If I were to connect an ignition coil directly to a battery

I drove a wrecker 3 years for AAA. Only ballast resistor I ever replaced was on a Chrysler product. Luckily as was mentioned they were usually behind the glovebox.

Actually, the solenoid just shot the full 12 volts to the coil when it engaged the starter. The resistor was elsewhere. Ford did the same thing with the starter relay on the fender panel because they used a Bendix Folo-Thru starter drive that didn't need a solenoid to engage.

The one behind the glovebox is the A/C Resistor Block. The Ballast resistor is in the engine compartment on the firewall either in the center or towards the passenger side usually.

Can you find my resistor? This was my old '52 Ford with a '55 Buick 322 V8. Car was 6V, engine 12V. Anyone remember center-tapping a battery?

Check out the thick Chrysler radiator!

You are correct, and I was wrong on the "R" terminal.

The "R" terminal on the solenoid is for Resistor by-pass.

The resistor that GM used on point ignition systems was, the unique resistance wire they used from the ignition switch to the coil.

Benesesso could probably explain the use of different alloys used in making wire that would create resistance and not get so hot as to turn into a toaster oven and melt the loom.

I'm trying to remember back 40 some odd years ago and, nichrome comes to mind as the type of wire GM used.

Good question--I don't know. Nichrome would work, but would be way out of its element. You don't want a red hot heating element inside an insulated wire. I know the white ceramic "dropping resistors" got good and warm, but the resistance wire didn't get red hot.

Yeah... my father called it nichrome... right after I bypassed the wiring harness on the Buick hit-to-pass race car I set up... had to pull as much as I could of that wire out of the harness and wire it back in. Never did understand why it had to be there until I read this thread. Makes sense now... thank you.

As for the heating bit... power out is volts * amps... a couple of volts drop on the minor current a coil would draw isn't going to amount to much power and thus heat.

David...

been a while since I fooled with a balast resistor, but ya, nicrome wire in ceramic is the way I remember it. so.... 2-3 amps of coil current and a 2 volt drop across the resistor is 4-6 watts. not all that much heat.

yes, I had a couple trucks with a dual post battery... we even had a company up here that made them. we also used to tap a screw into the cell connector between 3rd & 4th cells to run the gauges. pretty much everything else was easy enough to convert. I even had a positive ground GMC truck once

Back in the day when the first OHV V-8s came out, they were all 6 volt. The old hemi Chryslers especially had cranking problems. We fixed a lot of them with what was sold as an ABCO Automatic Battery. It was a 12 volt battery that was split into two 6 volt halves, and had a couple of relays mounted on the terminals. You ran a wire to the starter relay to activate the battery relays when the starter was engaged, they connected the two 6 volt sections in series, and the engine cranked on 12 volts. When the key was released, the sections were re-connected in parallel, and the car ran and charged the battery on 6 volts.

BTW, 6 volt Fords were positive ground.

You can get a coil with a built in ressitor. that what i did when i had to redo something once never had a problem

Not all 12 volt coils need a resistor. Some are wound to operate on 12 volts and have no resistor inside. Using one on a system that has a ballast resistor would have that 12 volt coil running on 6 or 7 volts and could cause ignition problems.