battery dies after a few hrs ??!! help..

[fongo]

Hi everyone. Thanks for your reponses on the previous thread. To recap, my battery dies after a few hrs at rest. Originally, I thought it was the battery and/or the voltage regulator. It turns out that after doing the battery / alernator test (i.e. disconnect battery after starting car and see if it still runs or stalls), the car continued to run so I assume the alternator is still good (??) unless the voltage regulator is bad and this test can't distinguish the problem.
Could it be the battery cable running from battery to starter or the other one? The car starts fine when everything is charged so I didn;t suspect this.
I also noticed the wire plug going to the alternator (top) seems a little old and unsheathed. I put electrical tape on it to see if problems goes away.
Any other possibilites and/or recommendations?? ( I hate to bother people to jump start me every time!)
Thanks.
fongo

[mpj76]

Does the battery seem to die all of a sudden or gradually. You can check by periodically looking at the headlights. If it dies gradually, maybe there's a short somewhere. If it dies all of a sudden, try shaking the battery a little and the wiring around it. I had a similar problem and it turned out to be that the wiring looked OK on the outside, but was corroded on the inside. It would be better or worse at times depending on very slight movements of the system. Sometimes it would turn over sluggishly or not at all. Sometimes the voltage needle would dip every time the turn signal flashed. I'm assuming you put a volt meter on the "dead" battery. Did you check the current coming out of the alternator? Keep in mind that the current output at idle probably isn't near the advertised max output. Perhaps the alternator is outputting just enough current to keep the car running, but not to charge the battery?

[Ieatcamaros]

Sounds to me like your alternator has a diode burnt out in it. It still charges while it's running, but discharges your battery when not running. Put a voltmeter on the battery while it's running and see what the voltage is. Should be at least 13 at idle. Since we're talking about a fox mustang here. Rev it up to like 1500 or 2000 and see if the voltage comes up to 14. If that looks to be ok, try disconnecting the positive cable while the car is sitting. If that does the trick, then you need a new alternator. It is easier to just replace the whole alternator rather than trying to replace just the diodes.

[speedytang]

Since it is a GT I would check the visor mirror lights. Mine was doing it for months kept removing fuses to find the voltage leak and late one night seen light in my car thru the sunroof. The visors warp and don't touch the button when the weather changes at night and make one of my visors to light up all night.

[289]

If it is a Good battery and you fully charge it and then hook it up to your car while off. then 3 hours later its dead the I agree with "Ieatcamaros" it is the rectifing diodes in the alternator.
I had this exact prob in my 88 stang
the car will charge half ass while reving the motor but idle or off it will drane your batt like a drunk at happy hour.
disconnect the alternator and let the car sit then reconnect it and see if it starts
The retifiers on these cars are shity they don't have a good heat sink and if you run anything that takes much juice they will give out after a while.
If you know how to take apart an alternater(which isn't hard) you will see a plastic part with 3 leads coming off it screwed to the back. This is the rectifier, if you go to your local alternator shop they should be able to test it for you and sell you another for like 25 bucks.
I think this is prob your problem
Good luck

[fongo]

Thanks everyone. It turn out it was my alternator slowly dying out. I popped in the PA peformance 95 amp replacement and WOW! what a difference! No more flickering headlights, bad A/C output etc. it comes with a do-it-yourself kit to rewire the stock setup. Very easy.
I recommend these products!!
fongo

[87prjctpony]

well bud... i have my 87 5.0 and when i barely had gotten it i thought it was normal the way it would start up (very Lazzy) and then i heard other ponies fire up and they would fire up right away!
i would run my car hard just 1st 2nd gear and stop, turn the car off and try to restart it and the battery would be dead! i was left with ????? i bought a new battery, that wast it. checked the alternator, that wasnt it. so someone told me to change my starter. i though ,"no it cant be my starter because when starters go bad they tend to grind., well i changed it and turned it on . wow it fired up better than ever. that was my problem. i would try that .