Without any warning, serpentine belt parted. Got home and accomplished belt, tensioner, idler replacement. As expected, got the red screen charging system alarm, but now it won't clear. Went to diagnostic mode and see voltage only at about 14.1 to 13.9 volts. So, alternator spun just fine during belt replacement, didn't notice any roughness or resistance to spinning. Just a weird coincidence, or should be looking at regulator replacement.
Oh, we are dealing with a 2003 C240 wagon 2wd 146K miles. Battery right at 18 months old. So, what do one and all think?
Patrick

 

Mystery revealed, had an outside source do a scan with Star, and in the process of doing so, all the previously mentioned alarms as well as some spurious ones that would appear from time to time cleared up. A reset of the cluster did the trick. I was cautioned that cluster failure could still happen and be ready for that one (dealer only procedure) but for now, no faults or alarms.
Patrick

 

When you went in, did you still have the red screen? Did the STAR what reset the cluster (what is that?) and got rid of the red screen?

 

Yes,red screen was active. From what I was told, reset with STAR cleared a spurious alarm. No trouble since, except for the spate of alarms that happen in freezing weather on initial startup. Also related to potential cluster failure. Aside from that, a happy little Benz.
Patrick

 

Thank you so much. I did have a STAR do a reset but didn't help. My next action would be to replace the whole alternator.....