Anyone here have any experience with headlights and relay issues.
Got a 01 RD688s that when the DRL relay is installed I have headlights that won’t cut off. Old relay was bad, replaced it with an updated factory replacement and now the lights won’t cut off. Pin 87a is always hot when relay is out. When probing with power probe and applying 12V to pins 30 and 85 I have low beams on one pin and high beams come on on another pin. Was told by my FIL that switch to left of dimmer controlled headlights only. Right side of dimmer knob does park lights. Coming from the car industry the way the relay pins are configured make no sense to me on this truck. I do not know if this truck is ground activated or power activated. I’ve tried doing continuity test with DVOM and have had inconclusive results. Same Flash to pass switch on top left corner works, headlights still remain on when the supposed headlight switch is disconnected. Headlights were working fine and then went out one day. Got a relay buddy to test relay and found it was bad, which turned into me replacing relay with AutoZone 5 pin, and then Volvo(Mack) relay with new part number since one in truck was superseded. At this point I don’t know if I have a bad switch or something else since lights still stay on when switch plug is disconnected. Only thing not working now is center cab light. Switch to left of dimmer turns on 2 outside cab lights, switch to right of dimmer turns on the 2 middle excluding the center cab light since we thing bulb is burned.
this may or may not help but the high beam button on turn signal combo switch does not do anything to lights, at this point it is INOP. A few days ago we had an issue where right turn signal was not working, relay would click 1 time and then stop. Left hand turn was working as normal. I disconnected 7 pin plug from turn switch and disturbed some wires and has been working since. Could this be a bad turn signal combo switch or should I look elsewhere?
I also ordered a USB drive from eBay with wiring diagrams for this truck, still waiting on diagrams but figured I ask on here first.
