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Discussion Starter · #1 ·
I own a 1997 Ford F350 7.3l Diesel Reg Cab XL. I bought it without license plate lights. I mean the harness was missing. I purchased some and was going to run them off the taillights.

Little back story, the truck had a utility body and was removed and had a standard 8ft bed installed. probably why I was missing the license plate light harness. Also to note i installed led lights in the headlights. Anyways, I have a harness underneath, near the spare tire. I wanted to to see what was getting power. With the engine off and the lights on. I started testing the plugs. one went to the towing(4pin plug) one went to(i assume was for the license plate lights) one was for the taillights and brake lights. So i checked the the one i think went to the LPI, it was two wire connector coming off the taillight harness. Nothing. Then I unplugged the taillights and brake lights plug. Using the test light, I went to test one of the prongs and my hand slipped and i made contact with two out of the 6 prongs and there was a small spark, like an arc. I didnt think any of it, because i was still getting power from each one. I plug the connectors back and noticed i dont have any lights in the rear. Then realized I dont have any lights in the front. The only thing that seemed to be working was the blinkers, except when I use the hazards, the front passenger blinker lights up.

I test the fuses, find out the fuse going into the exterior lamps etc was blown, I replaced it. No change. Tested all the fuses under the hood, All good. Used a multi-meter, measure voltage on all the fuses, and they were good. Used the meter on the rear plug I arced and the reading are low, by a whole voltage. I unplugged my LEDs and used the stock bulbs, they came back on but barely.

Now for the strange part, for some reason I thought if I started the motor, it would solve my issue lol well... Once the motor was running, I press the brake, engine dies, I restart the motor, try pulling the switch for the lights, engine dies. Only time they do work, is i have the engine revved up to 1500rpms for a min, i cant press the brake, turn the lights on and engine stays running. Few things i noticed was my drivers side headlight was far dimmer than the passengers. and my engine wasnt warmed up but my alternator was hot to the touch. My headers and block were still cold. I ran a test using tool, cant remember the name, basically hooks up to one of your batteries, I used my passenger one. Run the motor at 1500rpm and let it do its thing. comes back to replace the diode in the alternator or basically replace the alternator. I dont think thats the issue because before i created this mess. the truck ran mint, no issues.

Most of my grounds except for one on the block looks corroded. I only could find one ground from the rear harness to the frame. near the spare tire. I took that off and cleaned it up with a wire brush. I looked around the plug, inside the plug and I dont see any burns or wires melted. Also engine off/key off, if the left turn signal is on, the brake light on the dash comes on and if I press the brake pedal, my left headlight turns on. I also cant start the truck with the brake pedal pressed or with the lights turned on. Just having the lights on and the key turned on/engine off. the check engine light comes out and the "wait to start" doesnt appear.

My theory is a short or a ground issue or wires melted and they are arcing. Is the ground in the rear suppose to be the only ground found on the beds side, plenty on the cab side.

Thanks for reading, I hope someone can help.
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