Wierd foglight problem - 2001 Surb 2500

Discussion in 'GM Electrical Tech' started by raueda1, Jul 17, 2011.

  1. raueda1

    raueda1 Member

    My foglights are dead and I can't figure it out. Maybe somebody can help. I replaced the relay and they worked for about 4 on-off cycles, then out again. Here's more info:
    • fuse is good. It was good all along, never blew.
    • There's power from fuse to the relay socket.
    • Jumping the relay contacts that power the foglights turns them on.
    • The relay itself tests good.
    • I unpugged the switch/button module and tested it. It's momentary contact switch and makes contact when button is depressed. so the switch seems OK.
    • Per the Haynes manual circuit diagram (called "Headlight system - typical") I hooked up jumpers to emulate the switch. Doesn't work, more evidence the the switch is OK.
    • Everything else electrical seems to work fine.
    My conclusion is that there's something someplace else that keeps the relay from powering up when the button is pushed. The whole system seems unnecessarily complex. It's wired through the headlight dimmer switch, park lamp relay (park lamps work OK), it's all controlled by the BCM (body control module?).

    Anybody had a similar problem? Anybody have a fix? Thanks!!
  2. sstoner911

    sstoner911 Epic Member 5+ Years 1000 Posts

    Maybe I am confused...but if your jumping the relay and it works doesn't that indicate a bad relay?
  3. raueda1

    raueda1 Member

    Not necessarily, and that's the point. I tested the relay separately. It closes when 12v is applied and the lamp circuit contacts open and close. the control signal TO the relay isn't activating for whatever reason.
  4. sstoner911

    sstoner911 Epic Member 5+ Years 1000 Posts

    The relay fixed the problem the first time....maybe try another just to rule it out for sure...if the relay fixes it again you have narrowed down the problem. There cant be too many things going on with it.

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