help! voltage drop 1990 k1500

Discussion in 'GM Electrical Tech' started by quicksilver8817, Oct 1, 2011.

  1. quicksilver8817

    quicksilver8817 Rockstar 100 Posts

    my voltage drops only when i accelerate to about the red line and battery light comes on and when i let off its all ok .. i had the system checked by a buddy at autozone and the battery alternator and started all checked out great so at this point im puzzled.. any input would be apreciated ..
  2. Caddiac

    Caddiac Epic Member 5+ Years 1000 Posts

    Belt slipping? Though I would expect you would hear it unless you have the stereo cranked and some butt kicking speakers.
  3. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    Time to take a close look at all the cables and grounds for the battery etc. Also the alt may be testing fine but a tester doesnt test the same loads that are under an alt when you are hard on the throttle and the voltage draw.
  4. dedmon27

    dedmon27 Rockstar 100 Posts

    x2 murdog. Regulator may be acting up intermitenly. Or the brushes are getting loose onthe stator due to the higher rpm's.
  5. SoundZman

    SoundZman Rockstar 100 Posts

    I would start with looking, possible replacing if it's been a good while, the serpentine belt, pulley & tensioner. I would never replace a belt without replacing the tensioner as they tend to wear at the same rate. I found shortly after doing mine that the pulley began squealing occasionally, so that's why I threw that in there.

    Try cleaning up all the grounding locations; bat to block, block to frame and cleaning the battery post. I personally added an additional ground cable from the firewall to the block. Nothing wrong at all with adding extra ground. Being that your truck is from 1990 I would highly consider replacing all those wires specially if they're OE. Wires can degrade over time even without having any visual indicators.

    You can try metering from your battery post to multiple different grounding locations to see if your getting different readings. Or you can try checking resistance from bat negative to block, frame, firewall, alt casing. You should IDEALLY have less then 0.5 ohms from any 1 ground point to another. I would personally be ok with seeing anything up to 1 ohm. Of course you want to check your meter first to make sure everything is reading properly before you begin.
  6. quicksilver8817

    quicksilver8817 Rockstar 100 Posts

    its still doing it ... the tensioner and idler are newer . grounds have been added due to the fact that i plow in the winter so i kinda had too. i plow so i know that kills batteries and alternators like crazy .. my best guess is the alternator.. i just cant get the damn thing to fault when its hooked up to the tester .. either way its lifetime warranty so i will be getting a new this weekend .. thanks guys
  7. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    Well you never mentioned it is a plow truck. then yes i say alternator right off... No ifs ands or buts since they get smoked FAST!!
  8. quicksilver8817

    quicksilver8817 Rockstar 100 Posts

    well i replaced the alternator under warranty yesterday and installed a brand new belt too! sadly its still doing it.. time to start checking all of my grounds :(
  9. quicksilver8817

    quicksilver8817 Rockstar 100 Posts

    well i checked some grounds an cleaned the can anyone give me a list of grounds that should be under my hood ? also is it possible that its just my battery causing all of this ?

    ---------- Post added at 07:49 PM ---------- Previous post was at 07:18 PM ----------

    also its worth mentioning that my motor seems to have full power when this happens .. only things ive noticed being affected by the voltage drop are .. head lights.. blower motor .. dome lamp and gauge lights ..
  10. quicksilver8817

    quicksilver8817 Rockstar 100 Posts

    Also it has been getting progressively worse ..

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