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Old Feb 23, 2026 | 05:05 PM
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Default Electrical problem

75 Coupe

I have a power drain in the courtesy light circuit. After killing a battery and having to replace it, I installed a blade switch on the battery negative, but that’s a temporary fix. My courtesy lights stay on the entire time I’m driving.

I know it’s the courtesy light circuit, found it by removing one fuse at a time with an ammeter between the negative cable and battery post. I have no clue how to find the problem. As far as I can tell, it is only the courtesy lights and cigar lighter on that circuit.

If anyone has any techniques to use to find the problem, I’d really appreciate it.

Thanks
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Old Feb 23, 2026 | 05:34 PM
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Headlight switch turned all the way counter clockwise?
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Old Feb 23, 2026 | 06:36 PM
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Or one of the door switches out of adjustment? Try manually pushing the switch plunger inwards, does the light go out? Try both doors. Remove the kick panel, inspect the wiring on the switch.
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Old Feb 24, 2026 | 09:12 AM
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Replace the fuse with a test light that has alligator clip leads. Now start wiggling wires You may have disintegrating insulation on a wire that is grounding out.
I’m
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Old Feb 24, 2026 | 01:24 PM
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Building on 4-vettes suggestion, reconnect the battery and verify the storage compartment light behind the seats is actually going out when the door is closed. That plunge switch failed on my 73 and the light never went out, but with all the doors closed I never saw it. Took me a few days to find it
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Old Feb 24, 2026 | 01:57 PM
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Thanks for all the replies.

I have checked and the headlight **** was not turned all the way. Also, checked the door plungers and nothing. I've looked at the wiring behind the kick panels, and nothing is obvious. Gonna check the storage compartment light today (hadn't thought of that one).

Odd thing, while driving yesterday, the key warning buzzer started going off for a while, then it quit. I can't remember if it worked properly before.

I'll report back.
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Old Feb 24, 2026 | 03:16 PM
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Well, I removed both door switches and the lights went out, but I'm stilling seeing 2.0 amps. Can't seem to get the door switches started back in the hole though, I've tried new ones and the old ones. Not worried about that now though.

How can I find where the 2.0 amp draw is?
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Old Feb 24, 2026 | 06:53 PM
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I was wrong, again. With the pin switches (front ones, not the Door Ajar ones) removed, and the wires taped up, the courtesy lights still light up. So I guess that's my 2 amp draw.

If I understand correctly, this circuit works by supplying power to the bulb and the pin switches provide the ground, correct? So it is grounding out somewhere. How can I find where?
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Old Feb 24, 2026 | 09:15 PM
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Yup, sounds like you have a pinched ground wire. Could be under the top trim, etc. Follow the wires.
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Old Feb 24, 2026 | 11:12 PM
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Originally Posted by Steve Stroman
I was wrong, again. With the pin switches (front ones, not the Door Ajar ones) removed, and the wires taped up, the courtesy lights still light up. So I guess that's my 2 amp draw.

If I understand correctly, this circuit works by supplying power to the bulb and the pin switches provide the ground, correct? So it is grounding out somewhere. How can I find where?
With the pin switches on the hinge side of the door removed, the courtesy lights can get ground from the ajar pin switches at the back of the door. Easy enough to prove by just pushing it with your thumb with the door open the lights should go out. If they dont then they are getting ground from somewhere else. Im working from a diagram for a 73 but I think your car is the same in this regard. But you mentioned the door buzzer was sounding off when you were driving, dont overlook that. But for the sake of looking at the easy points of failure, pull the factory anti-theft relay and check the anti theft pin switch under the hood.
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Old Feb 25, 2026 | 04:18 PM
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Originally Posted by 4-vettes
Yup, sounds like you have a pinched ground wire. Could be under the top trim, etc. Follow the wires.
I'm not sure what you mean by "top trim", could you elaborate?

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Old Feb 25, 2026 | 04:19 PM
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Originally Posted by ZIOGEO
But for the sake of looking at the easy points of failure, pull the factory anti-theft relay and check the anti theft pin switch under the hood.
Where would I find the anti-theft relay?
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Old Feb 26, 2026 | 11:31 PM
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There's a glove box light too - are you sure it's shutting off when the lid is closed?
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Old Feb 27, 2026 | 02:07 PM
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Originally Posted by barkingrats
There's a glove box light too - are you sure it's shutting off when the lid is closed?
Yes, I verified this from the previous comment.

I have also verified that the 'Door Ajar' light and switches operate properly.
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