The battery/alternator light on my 2005 C230 comes on frequently, but does not stay on. I stopped by an auto parts store who tested both the battery and alternator-both tested good. Any suggestions?
Thanks!

 

Maybe the alternator regulator? It screws onto the back of the alternator with a couple of cross head screws. It should come with a new alternator but can also be replaced seperately.

 

Thanks for the fast reply!! If the VR was bad, wouldn't the alternator itself test bad as the Vr is attached to it?

 

Not if this is an intermittant problem. It could be an electronic fault with the regulator opposed to an actual regulating fault.

This fault could be caused by many things though, it could be a wiring fault, a rubbed through wire shorting on something for example, or it could still be the alternator itself. It is very difficult to diagnose intermittant problems, becase the faulting part could not be faulting when you test it and it will test good!

This is a difficult one without me having the vehicle to work on!