Foglights short, low beams die?

Topic: Foglights short, low beams die? (Read 1026 times) previous topic - next topic

Foglights short, low beams die?

October 16, 2006, 04:45:27 PM

First, both my headlights and foglights are run off relays. My foglight switch won't do anything unless my low beams are on (wired from lowbeams on the headlight switch). About a month ago I was driving along and I noticed my foglights were off. Then they came on and my headlights were off but my foglights were on. After trying to figure it out, while driving, they both went out. Turning the switch off for a minute and back on, the lights came on again, but only for a few seconds. At this point, the bulb in the foglight switch was still lit but neither my fogs or lowbeams were lighting up anymore. Switch it over to highbeams and drove home like that.

Finally get the thing pulled apart and find that the headlights aren't shorting, but the foglights are. The 30A foglight fuse (with 10 gauge wiring) wasn't blown. the foglight relay was pretty warm but after disconnecting the foglights, it still functions normally (using a multimeter). The low beam headlight relay is fried. Did a couple more small tests and had to give up for the night, so I just left the foglights disconnected and swapped the highbeam/lowbeam relays to give me my low beams back. For whatever reason, all my wiring to the foglights checks out but both pigtails at the lamps themselves are shorted.

Haven't looked into it since, so I've been driving around with only my lowbeams on a good relay.

Just curious, anyone have any idea how this could have happened? I don't see how the current could travel down the "switching" wire for the foglights, to the foglight switch, to the headlight switch, and back to the headlight relay through the "switch" wire. Doesn't make physical sense, but it appears to have happened. The wiring for the two different sets of lights aren't near one another and only share the switch in common. They don't share any other power paths other than the source - the battery. The switches themselves both still work normally.

Ideas as to what happened and how? I'm going to dig into it later this week and I hope it hasn't "magically" fixed itself.

Foglights short, low beams die?

Reply #1 – October 16, 2006, 05:50:13 PM

Is this stock wiring? If not can you post a wiring diagram of what you have?

What is fried on the relay, the coil or the contacts?

"The fog lights are shorted at the pig tail wire." Does this mean you are measuring through the bulb filaments with an ohm meter? Bulb filaments will read a very low resistance with an ohm meter.

Foglights short, low beams die?

Reply #2 – October 20, 2006, 05:44:04 PM

Or something like that. Looked at it last night and the foglights can come on with the highbeams also - since thats taken care of in another switch. So ignore that part of the diagram, all 3 switch leads are coming off of one contact on the headlamp switch.

Contacts are fine, coil is bad I guess. There's no voltage being put through on 30 when 12v is given to 86. I measured without the bulbs being in and had continuity on the foot of pigtail coming out of the foglight housing so the wires are/were (replaced) shorting. I just don't understand how this didn't blow the fuse and killed the headlights' relay.

I have since switched to a 15A fuse since its more appropriate for 55w foglights but still surprised that the 30A didn't blow.

Foglights short, low beams die?

Reply #3 – October 20, 2006, 06:03:54 PM

PM or e-mail Jeff K over at NATO.

BTW, you still want those fender moldings?

Foglights short, low beams die?

Reply #4 – October 20, 2006, 07:24:02 PM

yeah, have emailed you a few times with no response

Foglights short, low beams die?

Reply #5 – October 22, 2006, 12:42:38 AM

I haven't gotten any e-mails from you at all. My Spam filter might be deleting them. Try it again if you want or else PM me. I'll be home tomorrow.