Thread: tracked down fault, battery warning light coming on

Over the last couple of days the battery warning light would come on and off, it would stay on for a while and after heavy acceleration would go off, then as the revs decreased on it would come again.
I pulled the bosch alt off and undid the rear plastic cover, after removing the brush holder I noticed one brush was shorter than the adjacent one, it looked to have been worn down faster, there wasn't much spring in the brushes. Then I noticed my fingers getting black for the carbon from the brushes, it was leaking out from the brush holder. I took to it with compressed air and found it removed a fair bit of carbon, as I blew the carbon out the brushed moved more freely in the brush holder and their length increased.

So it was the worn carbon dust wedging the brushes in the brush holder, stopping their springs pushing them correctly to make contact.
Easy fix that took no time at all, I thought I would share it.

Originally Posted by justinc

What were the slip rings looking like? That carbon dust is a product of wear/ arcing. The slip rings on the rear of the rotor where the brushes run will also wear away and pit.

JC

The slip rings looked ok, it'll suffice for the time being.
Even at wholesale, I don't want to spend what a New Bosch Alt costs. And wasn't interested in aftermarket no name chinese jobs at half the price.
I think I'll replace the slip rings and new brushes later.