Alternator Testing... Need advice

[minny]

Can I use the alternator with the free-wheeling pulley for the manual cars on my tiptronic that usually has the fixed pulley? I've been offered a refurbished Bosch free-wheeling pulley one for half the price of one with the fixed pulley due to surplus stock. If not can I swap the pulleys over from my existing alternator to the new one?

[RFM]

Yes you can use an alternator with freewheel pulley instead of a solid without any technical adjustment.

[minny]

Thank you.

[JFP in PA]

I wuold still take the time to check the cables; bad cables will not only continue the problem, they can also hurt the new alternator. A few min. with a multimeter is all it takes to test the cables for excessive resistance.

[Silver_TT]

Agree with JFP as I just went through this myself a few months ago and he was very helpful in helping me get it sorted. The cable harness from the alternator to the starter is known as a weakness in the 996 and 997s... and this especially manifests itself in extreme temperatures like it did to me this summer when it was 100+ F for multiple days.

To Lograys's point about testing (Logray, like JFP, is also one of the more knowledgable around here), just be careful of having your alternator tested at a place like Napa or Autozone. I replaced my voltage regulator in my alternator since it seemed like it was just that....and then had the alternator tested there. They passed the alternator saying it was fine and I assumed that the voltage regulator was all it was bercause a lot of the problems went away. However they didn't all go away....it turned out that the alternator wasn't working 100% at all RPM levels and I continued to have minor issues until I replaced the alternator. The alternator is pretty easy to get to, but not always very fun to get in and out. In the future I will probably just bite the bullet and spend the extra $300 to replace the whole alternator at first problem isolated to it. My car had 90K+ miles on it anyway with the original alternator, so throwing a new one in there probably wasn't the worst thing in the world.

Edited December 24, 2012 by ferrugia

[minny]

I've checked the voltages at different points - when the alternator is pushing out 13.8v, it reads 13.8v at the engine bay power point and the cable connection next to the tip box and 13.65v at the battery so there is a slight voltage difference.

Voltage difference from +ve battery terminal to engine bay power point is about 0.1v. Resistance from +ve battery lead to alternator is 0.2 ohms. There is no resistance from alternator body to body ground.