mechanics, need help. there is a short on my truck?

i have a suburban 2003. it has a short that drains my battery overnight. i disconnected the negative terminal on my battery and used a fuse tester connected to the negative terminal and on the battery the light of it turns on. it is supposed to turn off when you pull out the fuse that is causing the short. i have pulled all the fuses and relays from under the hood, and the fuses too from inside the truck. the light still stays on. i even disconnected the instrument cluster and the light still on, meaning my truck still has a short. any suggestions? what is draining my battery that i can't find? i have to disconnect the battery every night to avoid being drain overnight.

3 Answers

Relevance
  • 1 month ago

    You can't check for voltage draw the way you are doing it. All the modules and computers have to "go to sleep" before you can test. You need an amp clamp that goes around the battery cables. Using a test light won't work. I'd start by taking the red cable off of the alternator and taping it up so it doesn't short out. Leave the battery cables on the battery and see if the vehicle starts in the morning. Many times a bad diode in the alternator drains a battery over night.

  • Anonymous
    1 month ago

    Pull the large gauge wire off the back of the alternator and see if that stops the draw. It's the charge line between the alternator and battery, if one of the rectifier diodes inside the alternator goes bad it can cause a constant drain.

  • arther
    Lv 5
    1 month ago

    Put the multi meter on dc amps connect it in series with negative battery terminal remove negative terminal, note how much current is being drawn start pulling fuses till you identify what circuit it is on then start disconnecting things on that circuit till you find whats causing the parasitic current.

    probably the alternator is my guess

Still have questions? Get answers by asking now.