Battery Drains Overnight..draws Over An Amp

Discussion in 'Fox 5.0 Mustang Tech' started by foxbodymike87, May 22, 2013.

  1. so i put a new battery in the car and started it up and everything works..next morning the thing is as dead as a doornail. put a multi meter to it and its at 6 volts.. so i did an amp draw test and its pulling 1.06 amps. And im pretty sure it should be like .50 or somewhere around there right? I pulled each fuse to zero in on the problem and i pulled every fuse out and still pulling over an amp. Could it be bad battery cables?
     
  2. With the ignition off, you should be pulling less than an amp. Do you have an aftermarket radio, amp or anything installed? Something is pulling consistent current.
     
  3. Theres no radio
     
  4. A good way to see what's pulling current is to use your amp meter and pull fuses one at a time and watch when the current draw stops. That will help you isolate the circuit with the problem. :bang:
     
  5. Typically it is something draining the battery. Small things like glove box or courtesy lights are often the culprits. If you have an aftermarket stereo or alarm system, it is also suspect.

    The ideal method is to disconnect the negative terminal, and connect a Digital Multimeter (DVM) between the negative terminal on the battery and the negative cable. Set the DVM on a low current scale of 2-5 amps if it doesn't auto range. Watch the current draw, and then start pulling out fuses. When you see a sudden drop in the current, that circuit is the likely culprit. Note that the computer, radio & clock will draw less than 1/10 amp to keep the settings alive.

    See http://assets.fluke.com/appnotes/automotive/beatbook.pdf. You will need the Adobe Acrobat viewer which is also a free download – http://www.adobe.com/products/acrobat/readstep2.html
     
  6. I did that..i ended up having all fuses out and still pulling current
     
  7. Disconnect the alterator output wire, and then try the D connector on the back of the alternator.
     
  8. Ok, what am i looking for when i check it?
     
  9. Is or was there ANY aftermarket sound or lighting ever installed in the car? Any additional relays anywhere?
     
  10. i got the car with no radio in it so i dont know. but all wires and everything look original. also the car has an emergency cut off switch behind the license plate. idk if that could do it?
     
  11. The same thing as in my first reply to your post. A reduction in current draw on the ammeter or multimeter when you disconnect the wire.
     
  12. There looks to be 3 wires on that connector..does it matter which i test? Also i have a trickle charger going to keep the battery alive and the alternator is hot..i thought someone ran the car but its only the alternator
     
  13. Check to see if any of the power/alternator wires are touching metal or grounding out. As mentioned by others, do a voltage drop test at the alternator.my guess is the wiring is fubared. Stock alternator and wiring or 3G? The stock wiring is notorious for problems.
     
  14. Looks like stock wiring and and alternator
     
  15. No exposed or chafed wires..everything is nicely loomed
     
  16. What I would do since you already did the fuse pull test would be charge up the battery, verify with volt meter that the battery is fully charged. Disconnect the alternator and let the car sit over night and check again to see if the battery's drained. If it is then obviously the alternator doesn't have an internal short causing the drain it's something else at that point. Might want to then take battery to autozone or whatever and have the battery load tested.
     
  17. The test mentioned above by all is called a Parasitic Load Test. Most info I find on this shows a normal high reading is >.05 amps.

    http://ww2.justanswer.com/uploads/JHoop/2009-08-24_141346_Parasitic_draw_test.pdf

    Being that you've had all fuses pulled and the problem still exist mean that it is elsewhere, like the alternator that you mentioned getting hot as one possibility. The shut-off circuitry at there rear is a place to do another disconnect to take it out of the loop.

    My hunch is that it is a defect in the alternator. Second: The bad battery theory if you didn't have the problem with the previous battery .

    Can't wait to hear the fix....

    Good luck with it.
     
  18. Thanks guys.. battery is at 12.58v and ive disconnected the alternator. We'll see what happens tomarrow
     
  19. jvCAegW.gif
     
  20. Ok, so i just checked battery voltage and its at 12.25 with the alternator unplugged..so i think its deff alternator related.