I've crumped three alternators in a row now in my '82 300CD. Replaced the first just after Xmas, the second only three weeks ago and the third has now failed. Battery tests good. Any ideas?

 

alternator 1 was in the car when I bought it two years ago. Diodes failed. Alternator two was diode/bearing failure. I haven't taken this one out yet (foot of snow on the ground and all).

Belt tension is good. I don't know what circuits in the instrument cluster could be bad. The battery light comes on when I start the car and goes out and stays out as soon as I give it some revs. The wires appear good but I haven't run a continuity check at all. The battery ground is a little corroded. It just seems odd that I would crump three in a row. The only similar factor is that each one has gone out about three days after I take a long drive somewhere.

 

Just a stab in the dark, but is it possible, that while the engine is running, vibration causes the battery ground fail, which in turn would keep the battery from providing the necessary load that the alternator requires? If that is the case, the diodes can quickly fail.

 

The battery ground is really my only guess.

 

Engine Ground strap is good. No resistance.

Voltage at alternator, starter and battery are the same. No rise with rpm. Junction strip on r. wheel well housing just in front of battery is really corroded. And alternator light and brake warning light both light up together and go out together?

 

new alternator installed. replaced the condenser on the back. old one was split. charge light is going out on start up now. so hopefully with new battery cable and new condenser this alternator will last. we'll see.

 

Did you Clean the Junction Block?

 

I ordered a new one, but I haven't done anything with the old one yet.