1988 Ford Mustang Electrical Problems - Forums at Modded Mustangs
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post #1 of 4 Old March 8th, 2009, 11:05 PM Thread Starter
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1988 Ford Mustang Electrical Problems

I have owned my Mustang for almost a year and a half.
When I had purchased the car, it was suffering from a poor battery and alternator. I would have dimmed lights when both the fogs and hi-beams were on. I removed my radio and speaker to help remedy for temporary relief.

About two weeks ago the car had died on me at school. I had to jump-start the car at least 4 times in order to drive about 2 blocks to park the vehicle. I purchased a new battery and installed it. I was able to get home, but the following day the vehicle would not start. I purchased a newer alternator from PA Performance with the upgraded power wire. However, the vehicle is still having problems where it won't start. If I was to turn the heat on, the vehicle would cut-off.

I removed my entire smog pump system and A/C system.

What other options do I have now?
I am afraid that I have a ground issue... am I out of luck?
What other parts might be faulty or what should I examine?
My ECU is not in the kick panel (purchased like this), it wouldn't be a problem if it lays on the rug?
I purchased an Alternator Tensioner Bracket from Pro 5.0, I am positive that there is more than enough tension applied to the belt.
If I was to purchase a volt meter, where exactly should I test?
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post #2 of 4 Old March 8th, 2009, 11:22 PM
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Do a battery load test..

just because it's a new battery doesn't mean it's charged. Sticking a fresh battery in a car with a weak alternator is a bad idea..

Check all connections on the charging harness and clean your grounds.

Now do a charging load test. Turn on heat, lights at same time
should not dip below 13v

weeee foooord!

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post #3 of 4 Old March 8th, 2009, 11:31 PM
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I had similar problems with mine a few years ago. It would run fine all day long, but when I shut it off, the battery would drain. I replaced the battery and alternator, and still had problems.

You can do this, this is how I traced it: To test to see if the system was drawing power when the engine was off, I turned the engine OFF, then took the negative battery cable off the battery. I got a test light, clipped one end to the battery, and touched the other end to the disconnected battery cable. The light was shining, which means something was drawing power somewhere with the ignition off. **If you have the cash to buy one, you could also use an ammeter instead of a test light.**

I narrowed it down by removing my fuse links one-by-one, and I eventually traced it to the computer relay, which is mounted right above the computer. Apparently it was stuck ON, and constantly powered the computer, even when the engine was off, and would drain a new battery overnight.

Also, you will find these to be VERY useful... I did.

Schematic, in color, of the Fuel & Alternator & Ignition & AC, for a 5.0, by TMoss:

Ignition Switch Wiring schematic, in color, by TMoss:

'87 2.3 Notch with +4 cylinder mod

Gas, Grass, or Ass.. nobody rides for free
Black Stang Crew Member #11

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post #4 of 4 Old March 9th, 2009, 02:19 AM
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get your charging system tested, see if the battery is getting a charging voltage from the alternator. my electrical problems were solved by a $30 voltage regulator.

1984 Ford Mustang LX

The Wheels are HAWT I know.
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