94 Mustang

[veakin]

Battery drains while running. Battery will be charged at 100% and after driving the car a couple of minutes the battery drains to 50%. Car continues to run, but after it is turned off it won't start again. Have replaced starter, starter solenoid, battery, battery cables and alternator. What else could it be?

 

[alleymad95GT]

Bad ground? Bad connection between the alternator and the battery? Bad alternator or battery (new ones can be bad from the store just like anything else)?

I would think it is somehting in the charging system...

 

[veakin]

Checked all that. Battery is getting 14amps while the car is running.

 

[SableSal]

Checked all that. Battery is getting 14amps while the car is running.

You mean 14 volts? My new alternator is getting 14.59 volts. my battery was replaced recently. How long have you had that battery?

 

[HISSIN50]

If the alternator really is putting out over 13.2V the whole time you have it running, the battery might have a bad cell.

Were any of your new parts bench tested before being installed? It's not uncommon to receive a bad alternator, battery or starter right out of the box.

At this point, if possible to safely do, you could take the car to a parts store for a dynamic test. Just have a jump pack ready (or some other means of restarting the car).

 

[veakin]

The battery is new. We have had it tested at Auto Zone and they said it was good. It was dying before we put the new battery in. He has checked all the connections. Everything was tested.

 

[HISSIN50]

Well if everything was tested and all the connections were tested, what's possibilities remain?

 

[veakin]

That's what I'm saying!!! I am ready to bang my head against a wall. I know my husband is going crazy over this.

 

[HISSIN50]

My point was that the testing needs to be done again. Does he have a DMM?

 

[veakin]

Yes, he does Thank you for your patience.

 

[steve schmalz]

charging problems

i went through this same thing. it took me 3 months to find the problem. after i changed everything from the battery to the starter.i was frustrated and physically traced all of the wires. i found a car alarm on top of my steering column. it was a pro 8 system. i took it out. i found where they had spliced the wires into their system. I put them all back together. end of all my electrical problems. i had no idea that the alarm was even there. the black box was about 2inx3in and it was zip tied to the top of the steering column. I would have never found it if i hadn't traced the wiring all of the way through the ignition system.

 

[HISSIN50]

How did the car alarm allow the car to start but then drain the battery while driving? That's not likely.

 

[99FiveOh]

Sounds like a bad diode in the alternator. And Autozone is the most incompetent auto parts store in the nation! Their alternator tester is a joke. An alternator with a bad diode will still show a good voltage but not have enough amps to sustain the battery and run the car at the same time. So the car borrows some power from the battery as you're driving around until it's dead.

Take the alternator to Advance auto parts or an actual alternator shop and have it tested properly. These charging systems are pretty resilient to aging and mileage, so it's probably something simple.

 

[veakin]

Tested to see if it had a drain by disconnecting negative battery cable and putting volt meter to post and cable. Pulled all the fuses and the only time it dipped was when I pulled the fuse for headlights etc (fuse under hood) and the fuse inside the car that is for inside lights, electric mirror etc. Drove it around the block and now the stupid, freaking battery is at 40%.

 

[HISSIN50]

You would use an ammeter in series between the cable and post, not a voltmeter (same device but different setting). What was the meter reading?

There's a chance that the reading would drop when you disconnect the alternator's charge cable if the alt does have a bad diode.