auto idiot (me) needs help re starting/electrical

I've read all of the posts and replies that sound similar to my problem, but none quite hit it right on. I hope someone out there can help me diagnose this problem.

1999 Intrepid ES with 100K+ miles. Just completed trip of about 2000 miles and only on the last day did the problem start: the engine wouldn't (start). We had been using a thermoelectric cooler plugged into cig lighter (only on when engine is on) and thought that had some how prevented the 2 mo. old battery from charging.

Jump started and everything was fine until we needed gas. Still would not start after driving many miles/hours. 2nd jump start and it took us home with no problems.

Next morning wife discovers light in back seat has been left on. Another jump start and I drive 45 mi/1 hr to work thinking with no extra electrical drain the battery would charge. Time to go home and car won't start again. Jumped it and it ran for a bit and quit. Jumped again and drove for 2 blocks and the engine quit. Before that point, everything in the car electrical seemed OK and no idiot lights came on dashboard. At that point, temperature control unit went nuts (turned itself on; would not accept changes from control buttons; trac light came on. I jumped it one more time and made it back to office parking lot.

This morning I get AAA to send a tow truck. Driver takes keys and the engine starts up like nothing was ever wrong. Towed it anyway to dealership service and it started again and ran several minutes with no problems; running a/c headlights, etc. It would not fail for the service writer. He said it would be $96 an hour to look for a problem and they might not find one. I left it there until I can get my wife to come down with me to drive it back home.

Can anyone tell me what might be wrong? Evidently the battery and alternator (that I thought would need replacing) are OK. Maybe something loose?

HELP! Any replies, please copy to my E-mail: j71950@yahoo.com

THANKS!

I had an almost identical problem in my last car (a 96 Ford Taurus). It turned out to be the alternator although we had to test it several times before we got a fail reading. There was some sort of intermittent wiring problem that caused it to work sometimes (like when the garage tested it!) and not others (like when I needed to get home from work).

I think it was related to the extra drain from the cig lighter. I didn't have a cooler unit, but I was using a lot of electronics on a regular basis. (charging cell phones, using notebook computer, portable dvd player, etc).

I replaced the alternator twice with a cheapo model, and kept having the same problem before finally paying out for the "heavy duty" model and never had another problem with it for the next two years before I sold the car.

The cooler drained the battery extremely low.It sounds to me like the alternator and battery are still good but the battery badly drained.I used to drive a tow truck for AAA and saw these symptoms often. Explaining it in layman’s terms its like this: A fully charged battery may have 1000 Cold Cranking Amps. Every time you start your car, the starter drains about 25-50 amps out of the battery. Driving your car around replaces the amps that were used to start the car but at a slow charge rate. People that do limited driving often have dead batteries because of this. The same thing could have happened with the power drain from the cooler. If the drain rate was drastically more than the charge rate, the car could easily run with a jump start with no problem, since the power is coming from another car, but not start on it’s own power from time to time. Remember that the starter is only used to start the car. Once the car is running it runs from the alternator, assisted by the battery, and the starter has no other function.If you put your battery on a slow charge over night (10 amps), it should make your problem go away. Basically you’re not restoring the charge fast enough for what you are draining (starting the car, lights left on, etc). The alternator by itself, charges very slowly. Driving it around for a couple of hours will get you a few good starts, but will eventually go back to a dead battery until it is fully charged through a charger, not the alternator.