The Stovebolt Site Forums The Parking Lot '60-'66 Trucks Resistance wire, what years.

Working with a 1964 C10 original. Trying to help my nephew figure out if he needs a ballast resistor. Can someone tell me what years, in the 60’s, chevy put in the resistance wire? And the color? Thanks.

Not sure about the exact years it was used, but a resistance wire is easy to recognize. Because of the heat it develops, the insulation is a braided fiberglass material, usually tan or dark brown in color. The wire is stiff, and only has a few strands, silvery in color. The (+) terminal at the coil will have this type of wire, plus a normal copper primary wire that can be traced to the "I" terminal on the starter solenoid. If you unwrap the covering on the engine wiring harness, you'll find that the resistance wire is very long, and doubles back on itself to have enough length to drop the voltage to the coil sufficiently.

During normal engine running, the voltage at the coil primary should be about 20% below battery terminal voltage. For instance, a 14.5 volt charging system voltage will drop to around 9.5-10 volts at the coil (+) terminal.
Jerry

I see you're in Tennessee so you might consider just using a resister coil which does away with all the other wires and ballast resister and just requires a regular wire from ignition switch to the coil. You cannot have a 12v by-pass with a resister coil so if hard starting or very cold weather a by-pass is sometimes needed.

My 1963 and my 1965 1/2T C10 truck’s have factory resistor wires.

Resistance wire was used from 1960 thru 1974

55.2 through 59 trucks used a ceramic type ballast resistor as did cars of that era. The resistance "wire" was introduced in the early 60's.
Your 64 truck came with a resistance wire unless someone changed it out for some type of HEI system that requires a full 12 volts to operate.
Fred

Thanks as usual guys. I don’t have eyes on truck as it’s at the lake house. If the resistance wire is not disabled I will do it and install ballast.

It has a weird covering and kind of large OD. It is possibly yellowish with black stripe. Of course, as you know, it's easy to find. One end at coil, other at ignition switch. It is folded back on itself to get the required length. I abandoned it and used ballast R. My 1960 had it.

Spreading the resistance out over several feet of wire makes a lot more sense than concentrating it all in one place with a ceramic resistor. The heat of a ceramic resistor can cause burns if anyone touches it, and those resistors are much more prone to burn-out than the wire type resistor. Using the wire type voltage drop is a MUCH better choice.
Jerry

Of course Jerry makes a good point about spreading the heat. I however am choosing to go the ballast resistor route. I have my reasons. If I were to bet on it, I would say the resistor wire is nichrome. The same wire you see glowing in electric heaters. I worked with nichrome building furnaces for metallurgical research in my youth. I remember it being hard to work with. Terminations are a pain.

Yes, the wire is nichrome. Dropping around 3-5 volts over approximately 6 feet of wire does not create enough heat to jeopardize the rest of the wires in the harness, particularly when heat-resistant insulation is used. Crimp connectors used for nichrome wire have a much longer barrel section than connectors used for copper wire, and they require different tools to make a good, low-resistance connection.
Jerry

FWIW my '64 C20 came with the resistance wire. It's a Pink Fabric Insulated wire. So at least you can be sure it's correct for your (Nephews) rig.

HTH

Chris