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  1. #1

    Default brake lights not working

    Hi guys, looking for some direction.
    On my 2003 Chev ls1500 4wd 1/2 ton pickup.

    Problem is my brake lights are not lighting when brake pedal is pushed. #rd brake light on back of cab does light.

    Bulbs look good and no blown fuses that I can find.

    Any ideas ar eappreciated.

  2. #2


    bulb looking good and being good are two different things. I've encountered bulbs that appear to be solid, but have failed. I recommend swapping bulbs with a known good to prove the bulb is good/bad, first.

    After that, you can connect a multimeter to the bulb plug to determine if the bulb is getting electricity. That'll give you a starting point for failure. You could even do the multimeter test first. Just put it to 12V and connect the tool to the bulb plug to complete the circuit. You should get anything from 11.5 to 14.2 volts, depending on the battery charge, and whether or not your engine is running with the alternator charging the system.
    2006 Vortec Max 1500
    -Custom Tune (389HP 440 Ft/lbs Trq - Dyno'd) | Volant CAI | Magnaflow Dual-in/out Exhaust w/3" stainless pipe tips | Fully Built Transmission w/ Red Eagle Clutches & Kolene Steels w/ Corvette Servos and Stage2 Shift Kit | 35K Tranny Cooler | Mobil 1 | Royal Purple Rear Diff
    -Spray-in Bed Liner
    -Premium Sound w/lifetime Satellite Radio | Leather | Sunroof | Heated Seats
    -Limbstriping from USING the truck (those are badges of honor)

  3. #3


    . If just the third light is working I would crawl under the truck and play with the connections where the rear harness connects to the harness from the front. It should be on a crossmember above where your spare tire is located. Those connections are known to corrode and cause issues.
    Last edited by Pikey; 03-26-2013 at 12:12 PM. Reason: spelling correction

    1995 Silverado 4x4
    6" BDS Suspension Lift-3" Body Lift-Add A Leaf in rear -Trailmaster SSV Shocks-Duel Steering Stabilizer Kit -AirAid Cold air intake-
    4.56 Gears with Detroit Auburn Locker-Pro-Comp Traction Bars with duel shocks-Aluminum Skid Plate Kit-38.5" x 16.5" Mickey Thompson Baja Claws-Constant Dropping fuel gauge

    2005 Yukon XL Jet Power Programmer, Bilstein Shocks, Bilstein rear springs, Helwig Anti-sway bars, EGR Window Visors, EGR Hood Shield, Denali Headlights, Headlight harness upgrade, GE NightHawk Bulbs, White Night Rear lighting system, Russell Braided SS brake lines, PowerStop Brake pads, PowerStop cross drilled and Slotted Rotors,
    2002 Silverado ext cab 2wd (Sold)
    2003 Yukon XL (Totaled)

  4. #4


    Thanks for the advice guys, seem to have found the problem. Replaced bulbs after cleaning socket,not that dirty, and all seems to be working!
    Kinda weird but we will see.

  5. #5


    Not weird at all. Happens more frequently than folks realize, though not frequently enough that any individual wouldn't likely encounter it more than once or twice in the life of a vehicle, if at all. The electrical connections get a patina of oxidation on them that prevents a solid electrical connection. The action of sliding the bulb in and out basically scraped off the patina and restores the connection. Re-seating the bulb basically "fixes" the problem. BTW, this is why dielectric grease is a good thing. It prevents oxidation of the components by prevent oxygen from reaching the metal.

    Some folks may question how the oxidation can occur between two contact points, and the answer is that the contact points aren't fixed. Heat expansion actually results in slight movement between the connection points eventually allowing oxidation to creep between the connection points. The vibration of a vehicle often prevents the connection points from actually getting enough oxidation (the vibration keeps the oxidation from forming too thick) to prevent solid electrical connection, but as you encountered "often" is not "always".

    Glad you found the problem. Cheers!


  6. #6


    Yes, it could have been corrosion, but, I suspect the two new bulbs fixed the problem. No, they didn't burn out together, one went first and then the 2nd followed shortly after. Bulbs have a defined life span, being used together, one will burn out and the other will quickly follow. You just didn't notice the first one being out, and then someone said "Hey, you don't have any brake lights".

    '09 Avalanche LTZ - Black
    '05 Envoy XL (sold)

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