12 volts to coil instead of 8, where is it coming from? - Team Camaro Tech
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post #1 of 11 (permalink) Old Jul 16th, 04, 06:56 AM Thread Starter
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I put a volt meter on my coil and did a test (stock 69 350 with factory wiring harness). When I turn the key to "on" it reads 8 volts. When I start the car it goes to 12 volts. Everything seems normal, but when I back the key off to "on" after engine is running, volts stay at 12 (or more, as engine revs).

The coil connector has 2 wires joined on one connector. 1 yellow wire and 1 black (with cloth resistor insulation on it. Since they are joined, I cannot seperate them to check indivual wires. The yellow wire is on the correct "R" stud on the starter seleniod. I did not follow the resistor wire back.

Are there any other testing procedure I can do to find out where the 12 volts is coming from? I am worried that the 12 volts will kill my nice 293 coil.

Thanks!

Kevin


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post #2 of 11 (permalink) Old Jul 16th, 04, 07:13 AM
 
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The cloth covered resistor wire goes to your fuse panel and is correct for the points ignition. It has to be replaced with a 12 AWG wire to run an HEI distributer. Eight volts with the key on should not pose a problem as long as you are getting a full 12 volts when running. You should be getting 13 - 15 volts at the alternator or at the battery while running.
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post #3 of 11 (permalink) Old Jul 16th, 04, 08:51 AM
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That's a stumper. Seems like if the solenoid was buggered up it would have 12 volts on the yellow wire all the time. I think I'd unhook the yellow wire from the starter and tape it up and do another test. At least that way you'd know which side was the problem.

Robert

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post #4 of 11 (permalink) Old Jul 16th, 04, 09:27 AM
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rojo has the right idea ... follow his advice... The solenoid is a big relay ... it seems to be sticking once it is energized. what is kind of odd is why the yellow isn't it just staying 12 volts all the time if bad...Take a measure on the purple starter wire once you release the key ... Could your switch be bad and allowing a low volt trickle ? This is a little speculation on my part, but I would defintely check it out. The purple wire should ony have voltage when the key is in the cranking position...Anyway, please be sure to post the solution once you track it down ...
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post #5 of 11 (permalink) Old Jul 16th, 04, 10:36 AM Thread Starter
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Thanks, I will do some more tests.

I should have 8 volts from the resistor wire all the time. And the R stud should show 12 volts at start, but not at run and the purple wire should have 0 volts when key "on" and 12 volts when starting and 0 volts running.

Right?

Kevin


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post #6 of 11 (permalink) Old Jul 16th, 04, 11:19 AM
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Right

Although the resister wire can show a little higher before starting and then should drop after running a few seconds.

Edit: The yellow wire will have voltage at run because it's hooked to the resister wire but it shouldn't be 12v

Robert

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post #7 of 11 (permalink) Old Jul 17th, 04, 11:39 AM
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This can get a little tricky. If the points are open the resistance wire will show 12 volts (ignition on). It needs the load of the coil to be at 8 volts. With the engine running the points are opening and closing, which will cause the voltage reading on the resistance wire to be higher then 8 volts.

Bob.
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post #8 of 11 (permalink) Old Jul 17th, 04, 12:22 PM
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I apologize if I was confusing earlier. If you do the test rojo recommended of disconnecting the yellow from coil, it should not be energized in the run position, only in the crank position. If the yellow is disconnected from the coil and it has 12 volts on it, it can only get it through the solenoid ... The solenoid does have 12 volts by way of the + battery cable; however, the 12 volts are not routed anywhere until the purple wire energizes the solenoid during cranking ... That's why it may possible that the relay to yellow is not disengaging...If you are getting a voltage leak on the purple wire or the solenoid relay is just not fully disengaging is could cause the circuit to yellow to remain live ... Plus, once your alternation starts working, yep, you should see more than 12 volts on any circuit that carries a 12v load ... You will be seeing the same thing a volt meter would see....
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post #9 of 11 (permalink) Old Jul 17th, 04, 02:06 PM Thread Starter
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Well, I disconnected the yellow wire from the soleniod (permanently connected at the coil with the resistor wire) and ran the tests.

Yellow wire disconnected = 8 volts in "on" 12 volts+ when running

R stud = 0 volts "on" 12 volts cranking, 0 volts running.

this leads me to believe the soleniod is fine and the 12 volts is coming through the resistor wire. It is strange that it is 8 volts in the "on" position, yet gets 12 volts from something other than soleniod when running.

I gotta find the other end of the resistor wire and check that.

Kevin


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post #10 of 11 (permalink) Old Jul 18th, 04, 05:19 AM
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Quote:
Originally posted by KevinW:
Kevin, before you go too much further, please read my previous post. As a double check remove the distributor cap and open the points (place a matchbook cover between the contacts).

Then with the ignition on measure the voltage at the coil. I'll bet it will be 12 volts. Then close the points (remove matchbook cover) and the voltage will go to 8.

Bob.
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post #11 of 11 (permalink) Old Jul 18th, 04, 08:33 AM Thread Starter
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Bob, I am checking the voltage with the engine running. But I will try that test with the engine off. Thanks

Kevin


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