I have a '99 35th Anniversary Limited Edition GT Convertible (automatic) with an ongoing electrical problem that is becoming a huge issue for me. It all started a few years ago...

I would hear a loud THUMP! through the speakers, and most times the car shut off. I would put it back in park and turn the key; all the gages would shoot to the right, then back to the left, and the car would start. Power surge, I thought.

At the same time, the battery was going dead. After a few batteries, I decided it was a parasitic drain, but I had no idea what was causing it.

I took it to the local Ford dealer. Because the problem was 'intermittent', they couldn't find anything wrong. Eventually someone said the alternator was bad. I let them replace it ($600+) and drove it away. Same problem. Thump! through the speakers, and car died. I brought it back, and argued for another two days. They wanted to start replacing parts without a plan. Finally gave up on them and went to a local garage.

This guy took one look under the hood and said he saw the problem. There were wires that had burned or melted. I'm not sure which ones, but he replaced them for $90 and everything was fine. The parasitic drain was still there, but I was just happy that everything else was okay.

So, for the last two years, I've been disconnecting the battery when she sits for more than a few days. We bought an '01 Cobra, and then an '06 Charger, so it's time to sell something.

I'm getting her all cleaned up, and took her in to yet another Ford dealer to have the wiring in the hand brake fixed and a fuse replace (the radio wasn't working.) Turns out the amplifier is shot, so they ordered a new one. They replaced the amp and said the wiring on the alternator was burned, but not a big problem since I was selling it anyway. In the meantime, the battery goes dead (of course.) I asked them to do a parasitic drain test, which came back with 20 milliamps, which they said was normal. They think the drain was caused by the bad amp.

On the way home...THUMP! through the amplifier, and car shuts off. Two days later, battery is dead...

So, I'm at my wits end now. What to do, what to do...

Any ideas? Anyone with a similar situation? I'm open to any thoughts
And thanks for taking the time to read such a lengthy problem.

 

Ouch[:@]

I'm guessing somewhere in your cars wiring harness the insulation has been rubbed off & live current is contacting ground,, maybe it either happens at a certain vibration level, or is heat (expansion) related. And when it does happen you hear it through your speakers.

Try pulling all the fuses that have anything to do with the sterio & drive it around a couple days. Leave the battey connected & see if the battery drain is still there

 

Thanks GreyStang. I'm trying to figure out which fuses go to the stereo according to the owners manual...not very clear which one's which, but I'll give it a try.

 

I called the Ford dealer and asked them what they thought the problem is. They seem to think that, due to the corrosion on the terminals and connections, there is a very high resistance between the battery and the alternator. They said these wires should be replaced, and will cost $209 for the wires, and 1 1/2 hours labor.

I'm sure those are the same wires that were replaced by the independent mechanic two years ago, so I think I'll take it back to him, although he never found the source of the parasitic drain (which might be the amp, now that it's replaced, we'll see)

Anyone want to buy a car?? She's real nice except...well...

 

I cleaned the battery terminals and so far, no problems! The battery hasn't run down, but a friend did a test and found the battery was losing juice at a higher rate than 20 milliamps.

She's at the same local mechanic as before for a leaky differential seal and to check the parasiticdrain again. And to check the wiring to see what caused the burned alternator wires.

I still love this car. Very pretty, clean, still has lots of get-up-n-go, good compression. Continues to turn heads and get attention. I want her mechanically sound before selling her.