Headlight Wiring W900

Something sounds off with your truck. Look at the schematic @Sublime supplied. Low beams should have power on 1 wire only with lows on. No power to the high beams. Trigger the high beams and power should switch over to the other wire on the low beams as well as be supplied to the power wire on the highbeams. The highbeams should only be 2 wires. Power and ground.

 

Since the OP never posted his location, is this maybe a Canadian truck with DRLs?

 

Well then something is F'd up. High beams should only have 2 wires.

 

Yeah. Even with DRL's there is only 2 wires to the highbeams. At this point the wiring sounds like a mess. You're almost better off hacking out the old wiring and starting fresh, following the schematic sublime posted.

 

If I recall correctly there 2 fuses for the headlights on a 97. One is low beam and one is high beam. I don't know if there are also 2 relays. I can there you for sure there is one fuse for all four headlights on my 93. It gets exciting on a 2 lane narrow twisting road when they all go out.