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Discussion Starter · #1 ·
Here is what happened today, the day i was getting ready to make a 1200 mile road trip...

Sitting in drive thru at the bank, i noticed my heater fan speed was fluctuating, then the radio started flickering on and off, interior lights flickering, then the idle started racing from 800-1700 ish, temp gauge went to hot side, oil pressure gauge to HIGH, everything electrical went haywire. I could barely get the car home due to the engine cutting out, then racing RPM's all on it's own regardless of the gas pedal. This is on a 86 Mustang GT all stock parts.

My initial thought was that my alternator had went bad. I got the car home and put the multimeter on the battery with the car not running and it tested at 12.9v. I started the car and the multimeter showed 14.6v so i deduce that the alternator is operating just fine. Any other ideas as to what the problem may be? Also of note is that it has been raining pretty good this morning, so something could have gotten wet i guess, but it shouldnt be doing something like this obviously. I suppose i can take the alternator off and down to the lcoal parts store to have it tested, but it seems like it must be working if the battery is getting 14.6v while engine running. So much for the trip to Vegas today :(
 

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You don't have to take it off the car to have it checked, probably be better to do it with it on the car. Then it can be tested with a load on it.
Is this the first time it happened? Sounds like something either got wet or fried.
 

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Might still be your alternator. I bought a new HD Ford battery from my dealership last year. The next day the car would'nt start. They gave me a second battery. It worked fine for 1 day and it went dead also. I called them and told them the alternator must be getting bad.

They tested the alternator on the car with a load and everything checked out fine. Next day, the battery goes dead yet again. After they gave me the 3rd battery they done quite a bit more testing this time and found out the alternator had an internal short; but it would only show up very periodically, even with the meter. After installing a 3G 130 Amp altenator, that was the end of my electrical problem. What a difference.
 

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Discussion Starter · #4 ·
Ok, so there is a ground wire from the battery to the body that is about 20 " long that at some point in this car's life, it had been cut and spliced. Whoever did this used SPEAKER WIRE. They of course had it covered with a lot of electrical tape running about the entire length of the patch so i had never noticed it before. This morning for whatever reason that splice gave way causing a short, melted a portion of the wire at the splice so there was a bad ground there. Put on a new wire, and good to go.
 
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