Taillight Stack/Marker Light Out - Possible Wiring Issue?

Discussion in 'Hummer Forum' started by BlackAvalanche03, May 13, 2017.

  1. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

    The one problem with a multi-meter and a brake light bulb, is that the bulb will have 2 filaments (one for brake and one for tail), so, brake can be open and the op could still see resistance.

    My suggestion is a couple of spare bulbs.

    BTW, as you said, water and voltage do not mix. There is a good probability that the bulb is burnt out
  2. Differently

    Differently Active Member 100 Posts

    That's a good point. I do believe however that on a duel filliment bulb the body is common ground and each filliment has a point sticking out from the body for power to that filliment. Checking each of those points to the bulb body should allow op to test each filliment. However bulbs are cheap and might be easier to just swap one in.
  3. Flyinfool

    Flyinfool Rockstar 100 Posts

    I have had bulbs fail with the element falling across the other element, An ohm meter said it was good but it was not good. In a pinch while out on the road with minimal tools handy I have tested bulbs using the trucks battery and a screwdriver for the connection. The bulb lighting up will tell you if it is good.
    You can also swap the bulb in question with one that is working correctly. If the problem follows the bulb it is a bad bulb, if the problem stays put then it is electrical.
    Water can take out a bulb, but it is not due to shorting, it is from the thermal shock of the water hitting a hot bulb, causing a sometimes microscopic crack and letting air into the bulb.
    Differently likes this.
  4. xPosTech

    xPosTech Epic Member 5+ Years 1000 Posts

    There's an easy way to turn the lights on/off from outside the vehicle when checking light bulbs. Rather than turning the lights on while changing bulbs and messing around with meters and possibly getting into a "Battery low - start vehicle" condition follow these steps.

    Ensure Approach Lighting option is on in the DIC
    Cover the Day/Night sensor at the center of the dash
    When you want to test any light Hit Unlock on your remote key fob - all exterior lights will come on
    To turn lights off hit Lock on the key fob

    This will allow you to turn lights on/off from outside the truck. No need to walk back and forth from the driver's door. The minimum on time is about 20 seconds but you can set longer times in the DIC. This turns on all exterior lights - even the backup lights. It was a real timesaver when I was installing auxiliary backup lights.

    Don't forget to uncover the day/night sensor.


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