I am working on a 320 4matic that yesterday got a burning smell and blue smoke in the cabin. Turns out that the blower motor resistor that we just changed a couple of months ago burned up. We are replacing that again today but, there is now a warning message in the dash for battery/alternator and the car seems to be stuck in the limp home mode. It will not shift out of first gear. Is there a way to reset this or should this car be taken to M.B. for service. Are the burning of the resistor and the limp home mode related, I wouldnt think they would be on the same circuit. Any help would be appreciated very much as I am leary to send this car to the one and only dealer in the state who is backed up and wont get to it for weeks. Thanks D

 

My guess would be that your system voltage dropped to the point where few control units will go inoperative for safety of the sensors and electronic circuits, as the transmission control module did. I would disconnect the battery, charge it up and reconnect it. You can leave the fuse for blower out to see if everything else is in working order and shifting should also be back to normal.
Good luck,
Bernard

 

Yesterday after posting here I decided to test the charging system and found that the alternator is charging at a rate of over 20 volts (yes I said 20 volts). My concern is that something in the transmission curcuit burned up. I think i am going to change the alternator and if things don't return to normal I am going to pass the ball to the MB dealer. Any suggetions? D

 

Yes, I believe you can change only the regulator part of your alternator by itself. It comes with new brushes and it is a lot cheaper then complete unit. Good luck, Bernard