So i tested 3 different alternators 2 of them were new and none of them seem to be charging. Theres power going into the main wire and also the pigtail wires that go into the alternator. Not sure if i missed connecting something during my rebuild i had taken everything out the engine bay to get it painted. Any ideas???

 

S4 or S5 car and which alternator?

 

sorry its an s5 and currently have a stock one installed.

 

The W/B wire has 2 volts or so w/key to on and wire connected to the alternator, which causes the idiot lights to turn on, and 12 volts w/key to on and wire unconnected (and then connected but w/the engine running). Also, out of box alternators from auto parts stores aren't always good to go.

 

is there any other connector or ground somewhere that would be part of the charging system? or is it pretty much what you covered so far?

 

The ground comes from mounting to the engine. And are you measuring the voltage output from the B+ wire or via a gauge? B+ gives a more reliable reading.

 

have the units tested, as satch mentioned we've seen quite a bit of issue with these remanufactured alternator quality. the alternator should self excite above 3500RPMs with just the charge wire attached and at least put out some voltage at that point, if neither are self exciting then they either have internal faults or the charge wire to the battery box isn't doing its job.

and last but not least double check voltages with a DVOM at the battery, do not trust the dash gauge.