I had a '92 140 chassis where the instrument cluster would flash its warning lights whenever the turn signals or wipers would be on. Very annoying so I sent the cluster to Programa in Florida for the repair and drove the car while it was out watching the speed limits carefully and filling the gas tank before removing!
Have also heard that b/c there were so many problems with these that MB has them rebuilt/exchange.

Good luck....
Tobias MB
4 MBs