A few weeks ago, I had an alternator belt fail on my 616 diesel 240D. I
replaced the belt, but now the alternator light stays on at idle and,
albeit faintly at cruise. At first it would go out at normal highway
cruise RPM. I have checked the belt for tension, and it seems to be OK,
but I have not precisely measured the tension.
Any ideas would be greatly appreciated.
Martin Joseph - 23 Nov 2005 18:44 GMT
> A few weeks ago, I had an alternator belt fail on my 616 diesel 240D. I
> replaced the belt, but now the alternator light stays on at idle and,
[quoted text clipped - 3 lines]
>
> Any ideas would be greatly appreciated.
Probably a slipping belt, but also could be something dragging which
caused the old belt to die and will kill the new one soon too!
randallbrink@adelphia.net - 23 Nov 2005 21:08 GMT
Well, there is no evidence of any slippage or dragging of the belt, but
then again, the W115 alternator is in a place where it is difficult to
see much of anything. Another part of the mystery is that
occaisionally, the alternator light will not come on when the
electrical (key)switch is turned on, but then will come on as soon as
the start switch is pulled. This could be related, or not, I do not
know, and the only manual I have, the Haynes, is mum on the subject.
coolmale48@hotmail.com - 23 Nov 2005 21:26 GMT
You might need new brushes on the alternator. Two screws take out the
regulator/brushes assembly (small black box on the lower rear of the
alternator). It's not expensive.
Your battery is likely discharging as a result, so hook up a charger
overnight if you have one. Don't overtighten the belt, or it will wear
the bearings.
Tiger - 23 Nov 2005 21:58 GMT
Measure the voltage to see if the alternator is putting out at least 13.5V
at idle... and 14.4 when revving at higher RPM. If not, you could try
changing the voltage regulator (aka brushes)... it is cheap to do.