Turn on headlights and tail lights go out. Need help!

Okay so the title explains most of the problem, there were some previous mechanics who have rigged the tail lights to work, i have checked all major components and found them to be good. The lights work in the back without the headlights on. Im not sure if its the drl interfering but it seems everything is centered around the brake switch and relay. Those 2 yellow wires are spliced and soldered in 2 locations. I have it rigged up for now but i need to know how to rewire most of it.. lol this is gonna be fun. I am not good with wiring diagrams

I'd say your headlight switch is at fault

Thats a possibility. Its one thing i have not checked, thanks! How would i check that??

With a test light. When the headlamps are on do the front park lamps light?

Bob L said:

With a test light. When the headlamps are on do the front park lamps light?

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The parking lights in front do work. Just to clarify the rear lights work when the headlamps are off, turn, back up, and blinkers all work. Im not sure if that could be insufficient ground but i did run a dedicated ground to the frame to see if that resolved the issue and it did not..

Earlier when driving with the headlamps on i noticed my cluster lights were out, turned the dial to turn them back on and it flashed on then turned off after about 5 seconds then wouldnt turn back on, so likely a bad switch, we will see tomorrow.. will post the results when i do the swap. Does anyone know where all the splices in the brake light wiring for the 2 yellow wires are supposed to be? Mine has 3 that i have found and all are home made, thinking that might be my problem. Usually 2 wires are 2 wires for a reason, and you dont just splice them to suit your needs, lol

Okay so to test this i went with a known good switch of a buddies to try it out with. No change. Cluster lights have yet to come back. Unsure what the problem could be. Im sure its in the loom now. I just need to run new evidently. Entire back section of wiring minus the third brake light (weirdly enough..) is colliding somehow with either running lights or something else when you turn on the headlamps. I know the brake switch and brake relay has been jury rigged to work so i would like to start there with this problem solving. But the issue is that the wiring is all piecemeal. Im 85% sure this is what my problem is. Under the dash there are 2 solders on yellow wires and under the hood near the relay there are 2 as well. I know there is only supposed to be one. But i need to know how that section of wiring is suppose to be ran.. the 2 yellow wires im questioning are the *hot side* of the brake switch relay.. i have checked the relay and confirmed it was ok. Any help would be awesome. Lol

Not positive but I thought tailamp wires were brown.

I had a problem on my 95 when the headlights were on the rear brake lights went on. I only did enough troubleshooting to 'fix' the problem for now by removing the center high mount stop lamp bulbs. I suspect a bad ground in the high mount circuit but it was too wet and cold to worry with until better weather.