White cloth-covered coil wire? 65 C10 292

[theastronaut]

There's a white, cloth-covered wire on the positive side of the coil on the '65 C10 I restored. It's got a 292 in it, if that makes any difference. The new repro harness doesn't have it and the wiring diagram doesn't show it either. If I remember correctly, it was wrapped up with the original wires in the wire wrap; could be wrong though. Anyone know what its for? Thanks in advance.

Here's the new harness. The green wire that goes to the starter is yellow on the original harness and also yellow in the wiring diagram I found.

[64fleetside]

The white cloth covered wire is a resistor wire to drop voltage to the coil after the engine has started-cranking=12v, running=6-9v-to keep the points happy longer.

You using points or some electronic ignition?

[theastronaut]

Originally Posted by 64fleetside

The white cloth covered wire is a resistor wire to drop voltage to the coil after the engine has started-cranking=12v, running=6-9v-to keep the points happy longer.

You using points or some electronic ignition?

Its got points in the original vac advance distributor. Will it hurt anything to run it with the new harness that doesn't have the resistor wire?

[bama63]

you can add a ballast resistor to cut the voltage to the points

[Captainfab]

I would hook it up first. Then once it is running, check the voltage at the coil and see where it is. Then you can change the wire or add a resistor if needed.

[HEI451]

IF that wire is silver stranded, it IS the ballast resistor. It is about 7-1/2 feet long, starts at the firewall connector and terminates at the coil positive terminal. Its resistance value is 1.80 +/- 0.01 percent ohms. Stock GM looms of that era used the silver stranded wire with white plastic "woven cloth" covering to indicate it was a point system feed resistor wire.

The earlier vehicles used a straight copper wire with NO white plastic woven cloth appearing cover, and a stand alone porcelain ballast resistor inline, instead of the resistor wire. That resistor is also 1.80 +/- 0.01 ohms resistance value, and is a NAPA part, or equivalent, ICR13.

To test that wire in your loom, use a digital ohm meter, set to read Rx1 ohms, and first, hold both meter wires together and read the scale. Digital meters will add a couple of three tenths of an ohm even if they are not reading any resistance, so, don't be surprised if the meter shows 0.40 ohms with both meter wires touching together. Then, read the wire and add the two readings. Lets say you found the meter to have 0.40 ohms, and you get 2..20 ohms resistance, subtract the meter operating ohms from the over all reading, and you fget the correct 1.80 ohms resistance value.

DO NOT RUN THE POINTS SYSTEM WITHOUT SOME SORT OF RESISTOR. Confirm there is the correct resistance, 1.80, or, the points will pit and burn very quickly, requiring replacement, and the resistance to be added to the circuit.

IF that wire in the loom IS NOT a resistance wire, then, go get the porcelain resistor mentioned above, and put it in line with the feed wire to the positive terminal of the coil.

Also, there should be another wire from the coil terminal of that wire in the loom, yellow if I remember correctly, that goes to the S terminal of the solenoid on the starter motor. It should NOT be a resistance wire, but a copper stranded, full continuity wire.

This can get a bit confusing as there were two ways GM did the bypass yellow wire from the solenoid to the coil. First method used the resistor wire from the firewall connector, through the loom, all the way down to the solenoid, then, the yellow copper wire from the solenoid to the coil. The other method used the resistor wire from the firewall connector to the coil, then the yellow wire from the coil to the solenoid. EITHER way works the same.

If you get stuck with this, let us now and we can help with it.

Usually, after market new wiring looms have either both a resistor wire and a copper wire to feed the coil, for use with either points/resisted electronic systems, AND, full copper wire for full battery voltage for more intense electronic ignition systems, such as the HEI, and others....OR, only the full copper straight voltage wire for electronic systems only. Your resistance check will tell which setup you have in that loom.

Hope this helps.

[theastronaut]

Thanks for the help guys! I unwrapped the original harness and the white wire is silver stranded and about the length that HEI451 said it would be. After looking over the new harness better, it does have a white cloth-covered, silver stranded wire that comes off the starter and goes to the firewall plug. The green wire that goes to the coil comes off of the white wire down at the starter. It looks like they just reversed the position of the green wire and the white wire. The only difference will be that the coil won't get 12v at start up.

[HEI451]

Not so, the coil WILL get a full battery voltage, "the full 12 volts" at start up.

Here's how it works.

When the ignition switch is in the 'run' position, voltage is supplied to the firewall connector from IGN 1 on the switch. From there, the resistor cuts the voltage as it goes to the solenoid, and then, up to the coil.

When the ignition switch is in the 'start' position, IGN 1 is disconnected, and no voltage is supplied from the ignition switch to the firewall connector and resistor wire. The R terminal on the solenoid IS engaged by the solenoid plunger to the full 12 volts at the ring that also runs the starter motor from the battery terminal on the solenoid, and that full 12 volts is in play, the coil gets that full 12 volts for fire up.

When the solenoid isn't running the starter motor, the R terminal is regulated by the voltage supplied by the IGN 1 terminal and the resistor wire. So, think of it this way:

IGN 1 is active, switch in run, coil is resisted, so is the R terminal. R terminal voltage will be the same as the coil, resisted

START is active, IGN 1 and resistor wire isn't powering the coil, R terminal is full 12 volt hot and supplies the coil with increased voltage for fire up. R terminal will show full voltage.

Sounds like you are in good shape, that is the way my wire-up setup is on my 1964 Chevy C30 1 ton dually flatbed, and it works correctly.

[theastronaut]

Originally Posted by HEI451

Not so, the coil WILL get a full battery voltage, "the full 12 volts" at start up.

Here's how it works.

When the ignition switch is in the 'run' position, voltage is supplied to the firewall connector from IGN 1 on the switch. From there, the resistor cuts the voltage as it goes to the solenoid, and then, up to the coil.

When the ignition switch is in the 'start' position, IGN 1 is disconnected, and no voltage is supplied from the ignition switch to the firewall connector and resistor wire. The R terminal on the solenoid IS engaged by the solenoid plunger to the full 12 volts at the ring that also runs the starter motor from the battery terminal on the solenoid, and that full 12 volts is in play, the coil gets that full 12 volts for fire up.

When the solenoid isn't running the starter motor, the R terminal is regulated by the voltage supplied by the IGN 1 terminal and the resistor wire. So, think of it this way:

IGN 1 is active, switch in run, coil is resisted, so is the R terminal. R terminal voltage will be the same as the coil, resisted

START is active, IGN 1 and resistor wire isn't powering the coil, R terminal is full 12 volt hot and supplies the coil with increased voltage for fire up. R terminal will show full voltage.

Sounds like you are in good shape, that is the way my wire-up setup is on my 1964 Chevy C30 1 ton dually flatbed, and it works correctly.

You are correct. A local mechanic that owns a few 64-66 trucks called today to ask how the resto was going and after telling him about the harness, he explained the same thing you just did. Thanks again, and I have alot to learn about the electrical system!

[HEI451]

The only thing to remember about electricity is, it can be very shocking, sometimes!