Peterbuilt

When the key is turned to START 12 volts is sent down the purple wire, that turns on the solenoid which turns on the starter.
When the starter is ON a disc (inside the solenoid) sends 12 volts UP the (yellow) wire from the "R: terminal.

When the key is in RUN the YELLOW wire sends 12 volts DOWN to the solenoid (because the BLACK- PINK and the YELLOW are connected at the coil) but the DISC is no longer engaged.
The YELLOW wire is LIVE but not now connected to any circuit.

Peterbuilt

The BLACK wire on the COIL gets 12 volts (battery voltage) only with the key in START or RUN.

jnb5101

Your meter itself is supplying the current to complete the continuity test. The points are closed and anywhere that you touch completes the circuit thru the coil, points and anywhere on the car. Disconnect the capacitor in the distributor-remove it from the hold down clamp and make sure it doesn't touch anything. Connect battery and turn ignition to "run". Test voltage from + to - side of coil. Then test from + coil to engine ground. Both should be exactly the same and be about 11 volts. If there's a difference, there is a bad connection in the distributor or the points are bad. If it reads 12 volts, you do not have a resistor in the circuit.

Wee

First thing I did was connect the black and red wire into one connection and put it back on the coil.

I took the capacitor out of the distributor but kept the wire from the - side of the coil hooked to the points....With points closed I get 6.4 volts reading from + side to - side of the coil...and 6.4 volts reading from + side of coil to body ground....With the points open I get 0 volts from + side of coil to - side and 12.54 volts from + side to engine ground.

Brian

jnb5101

That proves that the coil wire has 12v. With the points open, there is an open circuit and your zero volt reading across the coil is correct. The 6.4 volt reading seems to be the problem. With the points closed and the ignition switch on "run", there should be about 11 volts from the + to the - terminals of the coil. Either the coil is bad, the points are burned or there is a bad connection in the circuit.
As a side note, it's important to measure the voltages with the points closed. If they are open, the meter will act to complete the circuit to ground, and since the internal resistance of the meter is several thousand ohms, the meter itself will act as the largest voltage drop. This will lead to confusing readings.

Wee

I'll pick up a new set of points tomorrow and report back on the readings.

I don't quite understand how the 2 wires work going to the + side of the coil....Forget what the stock color of wires are supposed to be....I have a single black wire running to the + side of the coil and it ran down the road just fine with just this wire attached....The red wire wasn't attached at all....If the red wire was in fact the resistance wire does it take over for the black wire and provide 11 or so volts or does it reduce the 12.5 volts being provided by the black wire....?

The points may be burnt up at this point which would explain my problem with the car dieing at a stoplight which brought this whole trouble shooting episode up in the first place...Fuel filter was stopped up and might also be the cause. I haven't tried to run the car down the road yet.

Thank Ya'll for the help...
Brian

Wee

Finally installed new points but the readings didn't change much, with the the capacitor still out of the distributor...

With points closed I get 6.21 volts reading from + side to - side of the coil...and 6.88 volts reading from + side of coil to body ground....With the points open I get 0 volts from + side of coil to - side and 12.54 volts from + side to engine ground.

Looks like I have another issue besides the points.

The next step I'm going to take is find out where the black wire is attached to.

Any other ideas....?

Brian

69427

I haven't gone back and re-read the first buncha posts, but the voltage readings you're seeing are normal readings for a points setup. Steady state readings with the points closed will typically show about 6 volts dropped across the ballast wire, and about the same 6 volts across the coil winding resistance (the coil inductance doesn't factor in at zero RPM). And, as you measured, when the points are open you will see battery voltage (12.5v) at the coil primary terminals.

Wee

I'll put her back together tomorrow, check the dwell and set the timing and she how she runs. I'll keep an extra set of points and tools to do the job in the car from now on.

Brian

TX-Techman

Peterbuilt it spot on, here is the diagram from my 69 (same as the 72 he posted), the yellow wire from the solenoid provides full 12 volts to coil only when the key is in start position. The black/pink wire is the ballast wire, it provides the lower voltage and has power anytime the key is in the on or start position. Both should be connected to the + on the coil. Sounds like the only wire hooked up on your car is the ballast wire, which means you do not get full voltage during starting which may cause hard starts.

If yours is not wired this way someone has made modifications that need to be corrected.

Stranger things have happened.

Wee

The black wire is not original, I know it has 12 volts in both run and start mode or it wouldn't have even ran with just it hooked up. I need to trace it down. The red wire I believe is original and I think is the ballast wire.

Guess I still got issues to work out.

Brian

Wee

Well I got everything back together today....Dwell set at 30. I didn't take it for a test drive because it was too late and I didn't want to take a chance on another break down. I did not get to set the timing, I don't have a light yet.

I know the volts won't read right with the motor running but I have read that somewhere around 9 volts is close....Well I'm around 4.8.

I didn't get a chance to trace where the black and red wire run to...Maybe tomorrow.

On a good note the the fuel line doesn't leak nor does the new heater hose fitting I installed....Now there is no interference between the fuel line and heater hose.

Brian