I'm having some charging issues with an 01 S60. When tested at the local auto parts store (tested at battery with car running) it comes up as failing the voltage regulator test but when I put it on a bench and test it, tests fine. The brushes look ok but the overrun clutch doesn't seem to be working properly.

A few questions.
- Can a bad clutch pulley cause charging issues at idle?
- How critical is the clutch pulley vs a fixed pulley?
- How common is failure of the pulley?

While I have the alternator out of the car I think I am going to go ahead and replace the regulator and bearings but I am iffy about replacing the clutch pulley. It just seems like something else to fail.