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No Brake Lights!

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by azaviator, Oct 6, 2013.

  1. azaviator

    azaviator New Member

    My '99 Suburban has not had brake lights for the last month or so. The tail lights, turn signals and flashers work. Third brake light doesn't work. My initial thought was the brake light switch behind the pedal but, on using the brake pedal, the cruise control suspends every time, so that has pointed me in a different direction. I've searched for ideas and came up with a faulty multi-function switch as the answer, so I ordered a new one. It came in yesterday and I spent 2 hours swapping it, but still no fix. At this point, short of replacing individual wires, I'm stumped as to what the fix should be.

    Wondering if anyone has additional ideas to keep me from pulling my hair out? I don't want to throw more money at it without knowing that it will fix the problem, but I need this vehicle to transport my kids around. Does anyone know for certain if the brake light switch is (or is not) the trigger for suspending the cruise control?

    All thoughts on this subject are welcome and will be entertained! Thanks for your help.
  2. BQS4

    BQS4 New Member

    You're kinda confusing, is it just the third brake light that's not working, or all your brake lights not working, just the running lights? If it's the third brake light, the one mounted on top, it may just be itself that's out. It's just a string of LED's running off the brake light circuit. If so, they can be had on Ebay and LMC Trucks online.
  3. RayVoy

    RayVoy Well-Known Member 2 Years 1000 Posts

    I don't have a wiring diagram for your truck. However, the "usual" way GM wires the brake light system is, from 12v through a fuse, through the switch (when pedal operated). to a junction where the circuit for the side brake lights is separated from the circuit for the center brake light. There may be a fuse before the split, or there may be two fuses after the split.

    Your observation that cruise suspends when the brake pedal is operated, is probably a good check of the switch; however............., you can not test an electrical circuit by guessing. There is a possibility, that the switch assembly may have two switch circuits inside. If there are two switches inside the case, one might be bad.

    Buy, and learn how to use, an inexpensive multi-meter.

    The first thing you should check is the lights. They are always the first thing to go, hell, they are designed to burn out.

    You could have two burned out brake lights and a bad center light, or a broken wire to the center light.
  4. azaviator

    azaviator New Member

    Fixed!

    As I was typing up my last question, I came to the realization that my testing of the brake switch was a bit incomplete. So I got down on my back under the dash (the worst part of working on a car, if you ask me) and got the electrical connector off the brake light switch. When tested with a multi-meter, the power (orange) wire had 12 volts. Then I used a jumper from the power wire to the brake light feed (white) wire. Low and behold, I had lights!

    Turns out the brake light switch has two circuits in it: one for the brake lights; one for the cruise control. The switch for the lights was bad. an hour later I had the new one installed and working like a charm! Problem solved, and with a lifetime warranty!

    Also, by replacing the multi-function switch, I fixed a problem I had with the intermittent settings on the windshield wipers, so I'm happy to have changed that as well.

    Thanks for the help.

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