84 Tail lights
Team Owner
Joined: Mar 2001
Posts: 54,124
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From: Cincinnati, Oh USA
Headlight switch off and fuse pulled, negative probe on ground, one side of the fuse will read 12v (hot all the time) and an ohmeter shouldn't be connected there(meter reading will have no meaning). The other side will read infinite resistance, this side gets switched to a lot of circuits with the headlight switched on and when you switch the headlight switch on, your ohmeter will show a short, or the same value resistance as touching the ohmeter probes together. Measuring across the fuse doesn't tell you anything of value.
You have a hard job because you will have to find where the shorted wire is and this involves checking each power wire going to:
Hazard switch, fog light sw, radio, inst cluster, front/rear marker lights, front/rear park turn lights, audio alarm module, license light.
Good luck, I feel for you!
You may not have an audio alarm, I'm going from my 87 electrical manual.
You have a hard job because you will have to find where the shorted wire is and this involves checking each power wire going to:
Hazard switch, fog light sw, radio, inst cluster, front/rear marker lights, front/rear park turn lights, audio alarm module, license light.
Good luck, I feel for you!
You may not have an audio alarm, I'm going from my 87 electrical manual.
Last edited by jfb; Feb 16, 2009 at 10:20 PM.
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jfb,
Thanks for the reply. You are correct measuring across the fuse is meaningless.
I removed the headlight switch to check its operation. This requires removing the dash which I am getting pretty good at. The manual says remove the instrument cluster but that goes nowhere. Anyway, after tracing the pins with colors in several manuals, I saw the switch is working correcting. The 12V comes in on the orange wire which is fused 10A. The power goes out the brown wire of the switch to the tail lights, front and rear parking lights, and license plate light. Measuring across this brown wire to ground gives 0.5 ohms. This would blow a 20A fuse. I guess I'll start pulling bulbs.
Thanks for the reply. You are correct measuring across the fuse is meaningless.
I removed the headlight switch to check its operation. This requires removing the dash which I am getting pretty good at. The manual says remove the instrument cluster but that goes nowhere. Anyway, after tracing the pins with colors in several manuals, I saw the switch is working correcting. The 12V comes in on the orange wire which is fused 10A. The power goes out the brown wire of the switch to the tail lights, front and rear parking lights, and license plate light. Measuring across this brown wire to ground gives 0.5 ohms. This would blow a 20A fuse. I guess I'll start pulling bulbs.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
The brown wire from the headlight switch goes to a large splice in the wiring harness above the steering column. All the wires from this splice are brown and go to the dash and front lights in my list. A brown wire from this splice goes to another large splice that powers the rear lights and this splice is in the wiring harness at the right rear of the car. All wires off this splice are brown.
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Joined: Dec 2008
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I went back to measure the resistance across the brown wire to ground and found it to be 10.5 ohms. This would give a current of less than 2 amps. I plugged the light switch back in and things work fine. I'm not sure what I did to fix it. I know the fuse kept blowing before and now it does not. Thanks for your advice.
