Strange Current Discharge..

[jobnetwork]

Have a weird one...

88 Mustang LX 5.0, new battery, new alternator, new cables. Even after changing all of the above, I'll be driving and the battery meter goes from the 3rd mark from the top all the way to the second red mark on the bottom. This is an instantaeous event and does not occur gradually. Usually after 15 minutes or so driving on the battery, the meter pops back to normal. But... occasionally it will run till the battery runs outta juice and the egine quits. This is really driving me nuts. I've tried pulling one fuse a time when it's in this mode but can seem to isolatee a particular circuit. Car is stock and does not have an electric fan... 100% of the time, early in the morning when first started, the meter is normal. Strange event seems tohappen as the engine warms later in the day. Livein moderate climate, San Diego, CA

Help!!!

Thanks

[PKRWUD]

I'm not sure what you did when you tried removing fuses to locate the problem, but the following is the method I always use (requires a non-powered 12 volt test light):

1) Turn off all electrical loads, close all doors, and remove the lightbulb from the underhood light, if equipped.
2) Disconnect the negative battery cable from the battery.
3) Attach the alligator clip from your test light to the battery cable post clamp.
4) Touch the tip of the tester to the negative battery post.

The test light should light, but be dull. If the test light is bright, you have a drain somewhere. You will need a helper for this next part.

1) Have an assistant hold the test light exactly the way it was when you did the previous test.
2) Climb inside the car, and get yourself into a position so that you can access the fuse panel with the doors closed.
3) Remove one fuse at a time, and have your assistant alert you if the test light dulls.
4) When it does, note which circuit the fuse was for, and start searching the loads on that circuit.

Take care,
-Chris

[jobnetwork]

Hi,

I'm sorry I didn't explain it well :-(

I actually installed an ampmeter
between the removed positive car lead and the positive battery terminal (in series) and had a 17A load (key on), removed one fuse at a time and load stayed constant. Load with key off approx .5A (stereo in hot standby).

Thanks
Brent

[gtsr515]

Sounds like a bad alternator to me, I know you said it was new, but, i work at AUTOZONE and we sell "bad", "new" alternators all the time, it sucks, but it happens. take it off, take it to autozone or somewhere else and have it tested. Also your gauge may be faulty as well. Check all grounds too.

[jobnetwork]

Thanks... Ya I've experienced those pesky bad new products...

But.. In this case,
Alternator on "spin test" generates 19.2V and maintains voltage within specs from 0A to 60A load. Alternator was even tested for over an hour. See why I'm goin crazy. I still think somethin somewhere has a huge direct but intermittant short.

Thanks for your help! BN