mustang keeps killing batterys...

fuzymealchosen1 · Jun 28, 2010

well it had a weird gel battery in it that was sitting for a few years so we thought it was the battery, so we took a battery out of another car that is prob a year old and we never had any problems with the battery.

we put it int he mustang then drove down to the muffler shop and back, i unplugged it right when we got home and now the battery is completely dead and wont recharge.

also when you leave the battery plugged in when its not running it will drain the battery in a few days.

im just wondering what this could be. the battery has been relocated to the back. could this be the problem?

also has a fairly new alternator

HISSIN50 · Jun 28, 2010

Test it for a parasitic draw. If you're over ~100 mA, something is up.

Good luck.

jrichker · Jun 28, 2010

Troubleshooting battery drains:

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 (100 MA) 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 – Adobe - Adobe Reader download - All versions

Strype · Jun 30, 2010

Or the alternator is not charging it...

tevans720 · Jun 30, 2010

Strype said:
Or the alternator is not charging it...

Don't think that has anything to do with it. He said when it sits for a few days without running it the battery loses power. With that said it is definitely a power draw from some where. The battery would only lose power while the car is on if the alternator was bad.

As jrichker said start testing and pulling fuses. If you have a amp and subs start with your amp(s). A bad amp connection is usually the problem.

Lawbreaker5.0 · Jun 30, 2010

If he is not driving far enough to charge the battery the alternator could play a roll but it does sound like a draw. I had the same thing happen on my 92 vert. I tracked it to a certain fuse and I would pull it if I new the car would sit for a long time.

SLO_5-OH · Jun 30, 2010

Doubtful this is your problem, but.........I had a similar problem with my 89 GT and it ended up being the vanity mirror light on the passenger side visor. Couldn't see or tell that the light was on until I noticed a very faint glow coming from my inside my car sitting in a completely dark garage. Check both vanity mirror lights to make sure they are off.

jrichker · Jun 30, 2010

slo 5-oh said:
Doubtful this is your problem, but.........I had a similar problem with my 89 GT and it ended up being the vanity mirror light on the passenger side visor. Couldn't see or tell that the light was on until I noticed a very faint glow coming from my inside my car sitting in a completely dark garage. Check both vanity mirror lights to make sure they are off.

Good diagnostic work!

This is an excellent example of how a current draw can be a simple sneaky thing that you really have to look for.

fuzymealchosen1 · Jul 1, 2010

slo 5-oh said:
Doubtful this is your problem, but.........I had a similar problem with my 89 GT and it ended up being the vanity mirror light on the passenger side visor. Couldn't see or tell that the light was on until I noticed a very faint glow coming from my inside my car sitting in a completely dark garage. Check both vanity mirror lights to make sure they are off.

ok thanks, ill try that

i know its not the alternator cuz the battery was at like 14 volts when the car was runnning

BPA · Jul 1, 2010

jrichker said:
Troubleshooting battery drains:

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 (100 MA) 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 – Adobe - Adobe Reader download - All versions

Do what he said and ignore everyone else.. Then let us know what fuse stopped the draw if you still are confused.

Strype · Jul 1, 2010

My buddy had this same thing happen on his thunderbird years back. It was really confusing too because sometimes when you'd get out of the car you'd get shocked

Turns out the dome light had become grounded out against something. You never know with these cars. On the 85-86 models the lights short out just behind the grill causing all sorts of problems. I once had to take my old 86 to an auto electric place and a wire to the power windows had grounded out inside the door.

Damn old fords

BPA said:
Do what he said and ignore everyone else.. Then let us know what fuse stopped the draw if you still are confused.

Oh mighty one

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