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Double check my electrical diagnosis of light issues on 65 Coupe

  • Thread starter Thread starter Duke City Novice
  • Start date Start date Jan 21, 2024
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    1965 coupe electrical issues
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Duke City Novice

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Mar 10, 2014
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Jan 21, 2024
#1
  • Jan 21, 2024
  • #1
I have a 1965 Coupe 200Ci 6 cylinder which I've tried to keep about as stock as possible. It's been a long slow build where I buy parts but due to time and motivation they sit for a long time before I get to try them out. After taking the car for a spin around the block, a major accomplishment for me, I have been wanting to button up all the electrical. I noticed that the underdash lights and the instrument panel lights weren't working. After trying many things I have come to the following diagnosis but wanted to run it past you to see if I have missed anything.

Tests:
1. I am getting power to the fuse panel and the fuses are fine. I did this with a light meter and didn't measure actual voltages though I can do that.
2. I pulled out a door switch and there is no power on the Green-Yellow wire which I think should always be hot from the battery.
3. I umpered power from the fuse to the Green-Yellow wire of the door switch and the underdash lights turned on.
4. I jumpered power from the fuse to the Black-Blue wire of the door switch which should run through the Light Switch and should also be a way of turning on the underdash lights and the lights turn on but I can't turn them off with the light switch. No dimming just full bright.
5. The light switch makes a faint clicking noise when I pull the knob out and turn it t0 supposedly brighten or dim the instrumental panel lights but no lights. Even in my darkened garage I don't see even the faintest of light. The bulbs all test fine.

My Diagnosis:
1. The fuse panel is bad. I hate this because I spent a lot of money on a new wiring harness about 7 years ago. I just don't see power for the lights getting out of the fuse panel. I also don't like this because i'm not seeing a fuse panel sold separately anywhere.
2. The light switch is faulty. I bought a new one about a year ago and they made the headlights work so thought I was good to go. But not being able to turn off the underdash lights and the instrument panel lights not working leads me to this conclusion.

Any other tests you'd recommend or anything I've missed? Before I throw money at the problem I've been trying to be as thorough and analytical as possible.

Thank you for any suggestions.

Duke City Novice
 

AeroCoupe

lube between the nut and the face. I know my lubes
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Feb 4, 2024
#2
  • Feb 4, 2024
  • #2
So do you have the wiring diagram for the wiring harness? Or can you tell us who made the harness and which one specifically you bought? This sounds like a simple project of tracing the wires and continuing to eliminate connections, slices, etc until you find the problem. These harness’s are super simple compared to newer cars so this should be hard to solve.

Remember, just because you bought a new part doesn’t mean it works.
 
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