Headlights switching on by themselves problem

MisterCruiser Feb 10, 2019

  1. MisterCruiser

    MisterCruiser Active Member I am in ireland

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    I've just encountered this problem on my 97 Colorado, got up the other morning and both headlights were on, stalk was in its proper "off" position and no keys in ignition. It had been raining and I suspect moisture got in somewhere. I disconnected the battery negative to troubleshoot it later as had to go to work (have another work car). Anyway, I connected the battery back up last night and the lights were off as normal. Then today, the same thing happened again, headlights came on by themselves with no key in ignition and stalk in its off position.

    The tail lights don't be on, it's just the front headlights. Whilst they were on today, I pulled each of the 2 headlight fuses under the bonnet and the respective left / right headlight went out. I didn't think to pull the relay, but I pulled it later when the problem wasn't present and it looks ok, I didn't open it, but the terminal contacts on it appear fine and the fuse box itself isn't wet or showing evidence of moisture.

    I tried wriggling random wires and wire looms, etc, to see if the headlights would turn on but they didn't.

    Where is the earth point connection for the headlights, is it an actual earth cable bolted to somewhere in the engine bay?
     
  2. Shayne

    Shayne Well-Known Member Guru

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    Rear bumper lights are known to rot and cause havoc in mysterious ways , i would look there first see it they are shorting out . If you choose to replace dont bother getting the cheaper ones from Milners they are a very poor fit , the ones i got from Roughtrax were good but its years since i bought them .

    As far as i'm aware i'm the only 90 owner on the forum who had to change the headlight control stalk at the steering wheel because mine failed .
     
  3. StarCruiser

    StarCruiser Well-Known Member Supporter Guru I am in uk

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    If there’s no sign of water, it’s unlikely to be water. If/when it does it again, try disconnecting the stalk plugs and see if that turns them off. If not, pull the relay and test for voltage on the coil pins. If none, try swapping the relay for a known good one, possibly it’s neighbour. If there is voltage to the coil pins replace the relay and wiggle wiring under the dash to see if they go out.

    Do you have a trailer socket installed?
     
  4. MisterCruiser

    MisterCruiser Active Member I am in ireland

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    Would the rear tail light units affect the front headlights? The rear lights wern't on, just the front dipped lights. I believe the headlights have a constant 12v and they are switched via the earth. I will check the rear lights though for good earths. Thanks for the tip to avoid the millners light units.

    I checked the main earth cable from the battery that goes to the top of the engine wing and also down to near the bottom side of the engine just above the sump, these 2 earth points seem good.

    When your steering wheel stalk failed, what were your sympton's, lights staying on or just no lights coming on, including indicators, etc??

    I have a trailer socket installed, I wired it up myself 5 years ago when I first purchased the cruiser, I had to tidy up some damaged wiring at the rear tail lights back then at the same time, then the fuse box randomly went on fire and burnt out a fuse for something to do with the tail lights, can't remember what exactly, I just got an auto electrician to fix it at the time, its been fine ever since. I'll double check the rear lights, I just never considered them being the issue as its the fronts only that are affected.
     
    Last edited: Feb 10, 2019
  5. Shayne

    Shayne Well-Known Member Guru

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    I struggle to remember now it was 6 years ago but i think using the indicators would turn the headlights off or they would only turn on very weakly , something like that .
     
  6. StarCruiser

    StarCruiser Well-Known Member Supporter Guru I am in uk

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    I’m not sure it will have anything to do with the headlights but I have had trailer socket buzzers cause random problems. I’d be looking around or above your burned fuse box for any damaged wiring that may be connecting to give you your fault.
     
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