Electrical issue. Distributor always hot

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jeremiahwarren17

Not-quite-so-new-guy
Jun 6, 2022
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Hey guys, I'm having trouble with my 1979 cutlass supreme. I have constant power to my distributor wire even when the key is turned off and other electricals (open door lights, dash lights) seemingly lost power. when I checked original fuse panel most fuses have 12 volts to them. Any ideas of what could cause this or what else I need to look into? Thanks in advance!
 

78Delta88

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May 23, 2022
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Did you get this figured out yet? The 79 was pre C3 system and has the HEI with Mechanical and Vacuum advance. If I remember correctly the switched ignition going to the distributor is PINK 14/16 G wire. Module should be the 4-spade connector, (2 on each side).

As far as parts replacement, most likely the issue is the ignition switch mounted inside the car near the bottom of the column. It is a pain to change but it is only held on by 2 screws 1/4 or 7/32. 1982 started the change to metric fasteners.

GM doubled up on their circuits, so when things got off spec, you would get back-feeds and problems like yours. 79 should have the spade style fuses and if the ignition fuse keeps popping this indicates a short and most likely in the switch on the column. The key switch operates the rod that engages the switch and closes the contacts to start the car. There is also a wire coming off the junction of the starter solenoid to energize the distributor during cranking.

On the older systems when the engine is cranking the distributor gets a full 12 volt supply from the solenoid and once the engine starts the distributor gets fed with 12 volts going through a resistor or resistance wire from the switch in the "RUN" position. This was necessary for point systems but not so much for HEI, yet this system carried through.

HEI will run as little as 9 volts, but when C3 came on scene the ECU (Computer) needs 10 volts to start and idle.

When you shut the key off, does the engine keep running?

If you disconnect the ignition switch do you still have 12 volts going to the distributor?
 

78Delta88

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May 23, 2022
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In talking about back-feeds in GM wires...

I once had a new 1985 Firebird still under warranty come in the shop, close the door radio goes off and dome light will not work, parking lights don't work. Open the door; Dome light comes on and now the radio works, but with way too much static interference. No one could figure it out.

Cause: A penny fell into the cigarette light hole on the console. Blew the fuse and cause all kinds of non-sense back feeds.

Fix: Removed the penny, replaced fuse, everything back to normal...

Another possibility is failed electronics in the alternator. Check and see if you disconnect the Alternator's 2-prong connector; does the voltage at the distributor go away?
 
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