Hi All. I'm working on a budget 740 Turbo "race" car (stripped out the interior, all unnecessary electrical items etc.) and I am now having a problem with the charging system. The situation is this: When I start the car, the alternator does not appear to be charging (the voltage stays around 12 volts and begins to decrease as the battery begins to drain). If I rev the engine up to about 4000+ RPM (ouch!), the alternator seems to "kick in" and work fine even after the RPM is dropped back down to idle. I can tell the alternator is now working because the voltage goes up to about 14 volts. Next time I turn off the car and re-start it, the same thing happens - no charging until I really rev up the engine, then things are fine again.

First, I suspected a bad battery (it was in fact bad - must have had a dead cell). I also swapped in another alternator (80-amp version instead of 100-amp version) while I still had the "bad" battery and the same thing happened. Now, with a new battery, I still have the same problem.

I'm thinking either A) the "bad" battery has somehow damaged both alternators, or B) there's some other odd problem with the wiring, but the charging circuit is so simple I find that hard to believe, or C) the "new" battery that I got has been sitting around on the shelf for so long that it is indeed "bad" as well (it was quite dusty, and only 11.8 volts when I got it, so I had to charge it for a while on the battery charger).

Does anyone have any ideas? I pulled the 80-amp alternator off and plan to have it bench tested, but I thought I'd put the question to the gurus first.

Regards,

Greg Sievert
Melbourne, Australia