I can't seem to figure out what is causing the drivers headlight to come on with the ignition switch. I've checked and can't find any places that have been tapped into. The headlight is brighter than the passenger side when they're both on also. I unplugged the harness under the hood and found the source is before that. I changed out the switch with the old one and that didn't make a difference. Any idea on where to go now?

 

The ignition circuit and headlight circuit are separate. The only thing they have in common is the battery. Check the fuse panel for crossed wires. I am assuming you have original wiring in the truck?

 

Yes everything is original except the added gauges which I did remove the lights to them to rule out that wire. I thought they were separate which is why I'm baffled on what's making the light power with the key, especially only one headlight and not both.

 

This may sound strange but one time time I forgot to reinstall the engine to firewall ground strap/wire and all sorts of strange things happened... like the EFI's electric fuel pump cycling when the headlight switch was pulled.

 

Maybe the problem is in the headlight itself? Have you swapped them to see if the brighter one moves when you do?

Might ck the dimmer switch elec connection?

 

I'll check those. I haven't moved the lights around, I have switched between high and low beam but no change in that