#1  
Old 09-06-2020, 08:49 PM
runningman runningman is offline
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Default coil voltage

I've been running the Pertronix I on my 67 GTO for almost 20 years and recently decided to go back to points. Installed new points, condenser, and coil, purchased from our host. Gapped the points and set dwell at 30 degrees and all good actually starts up better. So out of curiosity I checked the volts at the coil (+ side to gnd) and I'm getting 11.8 volts instead of the 8 or so that i thought it should be. It does have the resistive wire. And I couldn't remember if i jumpered IGN 1 and IGN2 somewhere for the Petronix so I ran a bypass from IGN1 using a resistive wire from an old harness (same length about 4 1/2 ft) to the coil and I'm still getting 11.8 volts when car is running. Shouldn't the voltage be lower? What could I be missing? There is 14 volts at the battery. Thanks in advance for any suggestions!

  #2  
Old 09-06-2020, 11:30 PM
Bill Hanlon's Avatar
Bill Hanlon Bill Hanlon is offline
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Assuming all the wiring is correct, with the key in the "on" position and the engine NOT running you should see battery voltage on the coil + (and on the coil -) when the points are open. The lower voltage (usually around 8 or 9 volts) will be seen on the coil + and zero volts on the coil - when the points are closed.

If the engine is running an analog voltmeter attached between coil + and ground will give an average of the 8 or 9 volts and the 13 or so volts that the alternator will be providing to the electrical system. If the engine is running a digital voltmeter attached between coil + and ground will typically bounce around all over the place.

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Last edited by Bill Hanlon; 09-06-2020 at 11:57 PM.
  #3  
Old 09-07-2020, 07:16 PM
runningman runningman is offline
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Thanks for the detailed explanation Bill it would seem the problem was in my testing not the installation. All is good with low voltage reading about 7 volts. Was able to enjoy Labor Day without thinking something went wrong! Thanks again.

  #4  
Old 09-11-2020, 01:27 PM
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HWYSTR455 HWYSTR455 is offline
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You could always run an external resistor if in question or didn't have an OE resistive wire. The Mopar ones are very inexpensive and last a long time.

Sometimes the resistive wires over time become 'more' resistive.
.

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