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back end lights do not work!

Discussion in 'Chevy Trucks' started by 79GmcBigRed, Aug 13, 2003.

  1. 79GmcBigRed

    79GmcBigRed Junior Member
    from dsghsd
    Messages: 6

    :realmad: ok heres the problem i got a 1979 Gmc pickup, shortbed with a 350. I replaced the brake light switch but still no lights in the rear end. i dont get turn signals either as well as back up lights. the fuses are all good. are there any immediate places i can look for this problem? But when i turn my headlights on I still get the running lights in the rear end just not brake, turn signals, or back up lights. Any help would be greatly appreciated:confused:
  2. 75gmck25

    75gmck25 Senior Member
    Messages: 119

    The first four places to check -
    There is an instrument panel ground wire that is connected to the top part of the bracket for the emergency brake pedal. If this is missing, it will cause problems with gauges, turn signals and other electrics.
    On the leftside tail light there is a ground wire underneath the tail light housing (you take the lens off, then four screws that hold the housing). This wire also goes across to the right side tail light.
    Behind the rear bumper is a four wire plug that connects the body wiring to the taillight wiriing. Sometimes the wires flex at this point and there are breaks in the wires.
    Under the hood on the driver's side firewall is where all the lighting wires come together and enter the fuse box. You need to check these wires to see if there is power at that point. If there is, then the wires under the truck are cut and you need to repair them. There is a color coded wiring diagram for the lights on www.chuckschevytruckpages.com.


    CARDOCTOR PlowSite.com Addict
    Messages: 1,312

    check wiring in back of truck
    usually it rots out specially if it had a trailer harness
    sliced into the harness

  4. Pelican

    Pelican 2000 Club Member
    Messages: 2,075

    You'll need to trace out the circuit, but first make sure the bulbs are OK. Sounds silly, but I once spent a few hours looking for a problem that turned out to be both bulbs blown at once. Check for a good ground there too.

    Your brake lights run through the turn signal switch, check both sides of this. From there it goes through a harness connector on the steering column and then the firewall. Check both sides of these. There's another connector behind the rear bumper, check this and if a trailer harness has been added, check this as well.

    If all these are OK, you'll have to look for a break in the wire somewhere, but check that the flasher unit is OK too.
  5. wyldman

    wyldman Member
    Messages: 3,265

    I'd check all the plugs under the truck first as suggested,as that is where I see most of the problems.Actually take them apart,as they will look fine on the outside,but the prongs will rot of internally.

    Don't poke at wires with a test light,as the little holes you make will let water and salt in and the wire will corrode off internally.Do all your testing at connections if possible.