Phantom Headlights (1 Viewer)

[86aggie]

This morning when my wife went out to walk, she came back in to tell me that my headlights were on and there was a buzzing noise. I thought someone had broken in and turned them on. When I got out there, the only lights that were on were the low beams. Clearly had been on for some time, given how dim they were. No marker or parking lights. It was locked. Turn signal switch was in full clockwise position - off. Turned the switch counterclockwise, all lights came on, turned it off and all lights, including headlights, went off. Battery was dead. Went back to bed. Went out just now and used my jumper box to start it right up, no problem.

I've got the ARB relay set up for the headlights - had it for 2+ years, with no issues. Thoughts on where to start looking? Could the switch in the stalk have a short?

 

[OSS]

Yes. Check the stalk.

 

[diesellibrarian]

Could the switch in the stalk have a short?

It could be, but having dismantled a stalk in an attempt to repair a similar-but-different headlight issue, I would be surprised if it was the stalk: I just don't see that many opportunities for a short circuit in the stalk switch.

I'm not an electrical expert, but the symptoms you describe seem consistent with a ground fault that may have occurred in a different circuit that caused that circuit to ground through the headlight circuit. There are a number of circuits that are connected to a common ground bus that's located behind the instrument cluster, and if there's a short and/or resistance on one of them, it could seek to ground through a different circuit with less resistance. I have seen evidence of this in my own truck: a burnt ground that was clearly the path of some kind of hard short at some point. It caused strange behaviour in my headlight circuit, including a buzzing relay (which can indicate high resistance and therefore reduced voltage on that circuit) and occasional instances of my headlights shutting off spontaneously while driving. Once I found the burnt ground and cleaned it up, the problems disappeared.

Anyway, I would clean all grounds and pull the instrument cluster to see if there is evidence of a short (melted wires, burnt plastic smell, etc.). An ohmmeter might be a handy tool for chasing bad grounds.