2003 C320 Charging
 

I'm a 300TD diesel head so I rarely come over to this side of the fence. My nephew emailed me last night with this question:My 2003 C320 Mercedes isn’t charging. I got a code P0563 – System High Voltage. I multi-metered the battery:1. engine off at 12.1V 2. engine on 11.3V 3. engine at 2000 RPM 11.1V I’d say it was the alternator, because the voltage didn’t climb above 15-18V. Voltage regulators are supposed to limit how high the voltage gets. The battery is 7 years old. I thought perhaps the P0563 was triggered due to the VR trying to get the voltage high enough to charge a marginal battery. Any opinions?

Generally this means the brushes are worn out. On my car you can just replace the regulator which has the brushes in it. However I think that has been "improved" on that car so you need a whole new alternator. But I don't have that car so I can't say for sure.

just replace the regulator
 

I thought the regulator was basically a group of diodes, but I have to admit no "modern" knowledge of vehicles past the late 80s. Would the regulator partyou speak of just have the brushes and the diodes on the same "plate" of sorts? I told him to just take the alternator to be bench tested, if anyone still does that. I've done brushes and bearings on Chevys long ago, and that was easy. I don't even know if you can get separate parts for MB alternators.

I beleive you can still get the regulator seperate from the dealer.

Well hopefully that is true. But I looked at a couple of sites that didn't seem to list the regulator.

PM sent to the OP (NoSparkNeeded)