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  1. #1
    Join Date
    Jan 2011
    Orange, California, United States

    Angry 1990 brake lights switch issuemm

    any suggestions on a 1990 gmc 3500 single cab long bed. my brake lights arent coming on but everything else works; ie, running lights, reverse, turn signals, hazards. i checked all the wires and conections and they all seem good, and i replaced the fuses

  2. #2
    stephan's Avatar
    Join Date
    Sep 2010
    Far West, Oregon USA,
    Blog Entries


    You replaced the fuses but did you check for power at the BL switch? Check it. If you do have power there, then bridge/jump the switch & check if they work. If they do, replace the switch. If not, then post back. I have a wiring diagram for an '88 C-3500 & I'll walk you through what to check next.
    1988 Chevy C-3500 2wd (no pic)
    350 c.i. 5.7 L Stock Block, 4 Bolt Mains
    L-31 Vortec Heads, Edelbrock Cam & Intake,
    Holley 650, Flowtech Headers, Magnaflow exh.
    Jet Trans 700R4, B&M Ratchet, 4:10 gears,
    3" susp. lift kit "shadetree"
    No rev limiter, No speed limiter lol

  3. #3


    We had a lot of problems with the stop lamp switches on those trucks when they were new. I wouldn't be surprised if your switch is bad. However, you should first check to see if it's properly adjusted. With the engine running so there's vacuum in the booster, press the brake pedal down as far as it will go. With the pedal down, find the little tab on the bottom of the switch and pull it all the way back. Release the pedal, and it's done. I've fixed MANY brake lamp problems by doing this simple adjustment.
    Good Luck and God Bless

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