Electrical Drain

Discussion in 'Fox 5.0 Mustang Tech' started by 89llx, Jun 13, 2014.

  1. I have an 89 lx , and if it sits for 3 days or more the bat will go dead
    But not if I unhook the bat first
    one more thing I made shure all the stuff was off ,like dome light, and took the fuses out one at a time, [shut the door ] and still got a small spark ,will striking the bat cable end to the bat post

    [Any Ideas of what to check,] the car only has 63000 miles and is rust free , if that helps

    #1 89llx, Jun 13, 2014
    Last edited: Jun 14, 2014
  2. Shutting the doors causes your battery to spark? That can't be good.
    Are you by chance running aftermarket audio equipment or an alarm?
  3. I think he means that he gets a spark at the battery terminal.

    What brand is your battery? I used to have a pepboys battery that was horrible, if the door was open for 10 minutes it would die.

    If i remember correctly, to check to see what circuit is drawing the power, you unhook the negative, check with tester from cable to ground post, then pull the fuses one by one checking each time for how much voltage is being drawn.
    stykthyn likes this.
  4. You need to check for a short.Disconnect the neg battery cable,connect a test light between the neg battery terminal and neg battery post,if the light is on you have a short.Have a assistant remove fuses 1 at a time and if the light goes out at anytime,that's the circuit with the short.Now reinsert the fuse so the test light comes on again,start disconnecting wiring harnesses from components in the circuit 1 at a time.If the light stays lit,reconnect that wiring harness and move to the next harness.Keep doing this until the light goes out.When you remove a harness that makes the light go out,the short is in that wiring harness or the component that you removed that wiring harness from is shorted.Step by step process will lead you to the short
  5. One thing you can try first as a quicker test(since its sparking when you shut the door)is disconnect the wiring harness from the dome light and see if it quit sparking.If not,disconnect the harness from the door jam switch(mounted close to the door hinges)to see if the sparking quits.If not,begin testing for shorts as stated in above posts
  6. Thanks Ill try that
  7. I tried that and my light went out on #8---courtesy lights,clock, key warning ,radio ,fuel filer door release, power mirror.

    How do I get to the back of the radio?


    Also I think this simple test works, I have 2 1989 mustangs. With the test light between the bat cable and battery, one mustang the light will NOT come on, but the one with the drain it comes on untill I pull #8 fuse, ---[ rockstarwb has come up with something]
    #7 89llx, Jun 14, 2014
    Last edited: Jun 15, 2014
  8. Easier way is to buy or borrow and digital multimeter that can read amps in DC. A lot only read up to 1AMP, you need to find one that can do 10A or so.

    DIsconnect one lead from the batter and hook the meter up in series (one lead to the terminal, one to the batt cable) and get a reading of how many amps you draw with everything off. Should be under 1 Amp.

    If you have more than that, start pulling fuses to isolate the circuit with the higher draw
  9. Thank you everyone !! I found it, glove box light was staying on
    stykthyn likes this.
  10. Glad you got it
  11. Thank you, Im glad too
  12. Good deal glad you found the problem