1987 Suburban Electrical Issues

Discussion in 'GM Electrical Tech' started by bigdaddyforge, Jul 2, 2009.

  1. bigdaddyforge

    bigdaddyforge New Member

    hey guys, n00b here. I'm the proud new owner of a 1987 Suburban/silverado r10/v10, but she's driving me nuts!

    haven't torn through her yet cause i'm still recovering from an accident that totaled my last car.

    I just replaced the alternator for a bad voltage regular because she wasn't charging. put the battery charger on it she starts beautifully for 1-2 days then it's dead.

    the volt gauge tells the tale of a short somewhere. with air, wipers, headlights, etc running and the truck in drive the voltage has dipped as low as 9-10v or as high as 14 with most items off (even with the new alternator)

    if i hit the horn the radio's clock turns off and the floor lights turns on and you hear/feel a buzzing in the wheel. even with the horn and raido fuses pulled it still happens.

    when the juice drops too low the wipers slow to a crawl. last night it seemed to spike back up to 14v to charge the battery and run the wipers at full speed in park with the air off. maybe the blower fan?

    just looking for ideas to run through with the volt meter, or that my guitarist can tear apart (I was an electrician for a few years, he builds guitar amps, and we're both computer engineers.....could be dangerous lol)

    any help would be appreciated. I'm just uber stressed with everything going on and would love this baby to be runnin' tip top and have one less thing to worry about.

  2. Springthing

    Springthing Epic Member 5+ Years 1000 Posts

    Oohhhhhhhh... electrical gremlins - my archenemy... all I can say is good luck! I hope someone here can help!
  3. bigdaddyforge

    bigdaddyforge New Member

    thanks chief, me too!

    some more info. windows and lights work fine and don't cause the voltage to move

    even the turn signal when it lights up the volt gauge drops like a 1/16 of an inch back and forth each blink.

    with the wipers and air off the voltage never moves below 13-14v so i'm guessing power feeding the dash or the wiring in the dash is burnt up. not sure if i'll be able to fix it myself anytime soon so it may end up in the shop. and the horn wiring is definitely ate up. even with the fuse out when ya press it the relay in the dash buzzes like a gameshow.

    not keen on a work truck with no air or wipers lol
  4. Crawdaddy

    Crawdaddy All hail the Mad King!! Staff Member 5+ Years 1000 Posts Platinum Contributor

    I've had issues with my 91 Suburban (same bodystyle as yours) where I'll sometimes block I think it's the D/L fuse. This causes some really werid issues such as the dome light not working when a door is opened, but works fine with it closed, and some other EXTREMELY weird issues. I'm not quite sure why things like that happen, but I think the fuseblock would be my first stop, particularly for that D/L fuse or something like that. Check 'em all while you're at it. As for the voltage dropping when any load is placed on it, the only thing I can think of would possibly be bad connection at the battery or elsewhere. Unless of course the new alternator is also bad, which sometimes happens.
  5. bigdaddyforge

    bigdaddyforge New Member

    thanks chief, i'll have to look at that. it's not *any* time a load is placed on it, only certain things. i can run the headlights, and highbeams all day long, but crank the air and the wipers and the voltage plummets.

    my guess was a short in the dash/fuse block as well, so i might see if i can con a buddy into doing it or just drop it in the shop for a day or two.
  6. jtriplett

    jtriplett New Member

    Considering the age of your truck, I suspect that corroded wires may be part of the problem. These would be most likely in the circuits that have high current demands (easily identified by the specified OEM fuse values). My 1999 Suburban has some serious corrosion on the door lock motor wires, which caused the motors to stop working.

    If it is at all feasible, I would consider a new wiring harness. Either OEM or from a company like Painless. this may sound a little extreme, but we all know how difficult electrical issues can be to solve.
  7. 2COR517

    2COR517 Epic Member 5+ Years 1000 Posts

    I would check all your grounds, starting at the battery. Check engine to frame, and frame to body. Make sure the cab is grounded also.
  8. bigdaddyforge

    bigdaddyforge New Member

    yeah, once i heal up from the accident i was considdering a painless kit if need be. i was thinking along the same lines that some wires may be corroded or the shielding has worn off and is grounding out somewhere on occasion.

    so far it seems to be working ok, but the wipers do slow down a bit and the voltage dips a little at idle. the door locks oddly enough lock, but don't unlock like the switches are bad (passenger side switch doesn't work at all, drivers side switch locks the doors).

    i might keep an eye on it for now and work on it myself as applicable. the more i think of it the less i wanna waste money in the shop since it's running.
  9. bob13

    bob13 Epic Member 5+ Years 1000 Posts

    Sounds like someone has been under the dash in the past or a lot of corrosion. Like the above post says I would check the fuse box. I had an issue like that awhile ago and the culprit was the main feed to the fuse box it was really corroded. After checking all the mains for corrosion I would run the truck and start pulling fuses one at a time, maybe it can single out the circuit.
  10. thrasher

    thrasher Rockstar 100 Posts

    Sounds like someone went at the wiring under the dash with a chainsaw!!!

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