HELP: Alternator Charging Issues...

[PowerHaus944Turbo]

I have a 1987 944 Turbo. I was driving at night and it seemed to be working fine, until I realized that I was driving on battery power. All too late I made this stunning realization was stranded. I got the car home, took the alternator off, and got it tested. It was fine. I put it back in and the system didn't charge at first. After a couple tries of starting it / disconnecting the battery to see if it would run, it began working again. I am very frustrated, to say the least.

Does anyone know any possible trouble spots that I can check? (wires, connectors, etc.)
My only hunch right now is that the field wire is faulty...

[Cebu]

Try adding and additional ground wire from chassis/frame or front strut tower bolt to engine. This seems to cure to many intermittent charging and instrument indication problems on the 944/951

[Jim Franks]

Powerhaus, don't disconnect the alternator with the car running. You WILL need a new alternator! You can fry the diode ring....at least. I don't know if you risk DME damage, or not. Don't take chances with an expensive system.

[cyclemike]

Powerhaus, you can field test the alternator with a screwdriver. The haynes manual has the procedure. I think all you have to do is put a screwdriver in the little hole in the side of the alternator while checking charging voltage at the battery with your meter. If you have the haynes manual, check it to make sure my method is correct. I don't feel like going out to the garage and digging mine up. (Just a shot anyway) Good luck.

[hawes99]

One way you can check to see if the alternator is working is to start the car, if you can, and then disconnect one cable from the battery. (I recommend the negative) If the car keeps running, then your alternator is okay. If not, you probably have a problem with either your alternator or a connection somewhere. Just as an idea you may want to check the cables that come off the starter. I disconnected my starter once and forgot to reconnect on cable and I had the exact same symptoms. I hope this all helps some.

Nate

[PowerHaus944Turbo]

My thanks to everyone that has replied to my message. I have had mixed results disconnecting the battery when the car is running (sometimes it works, sometimes it dies). I will try to check the cabling further, but I believe the problem may actually be temperature related... in that case I will ultimately have to get a new alternator.

[PowerHaus944Turbo]

I figured it out folks... And let this be a warning to all. I have a racing starter kill switch (the red switch comes out) installed near the battery -> It was bad!!!