I purchased a 1991 MB 500SL Roadster in July 2010. It has only 54000 miles, documented. In Aug 2010, I was driving home at 35 miles mph when the vehicle began slowing down to 10mph. The ASR light came on, and it took me 25 minutes to drive 5 miles to get home. I checked the owners manual. It talked about limp mode,ABS and loss of traction. The road was dry. I had the car checked over at a private MB mechanic. They said they could not find a code or a stored code for the ASR light. I went to the internet and found out that the ASR I & II had no codes for the ASR light or ABS. I checked with another private MB mechanic. His first thoughts were that the OVERVOLTAGE RELAY WAS THE PROBLEM. I also had a thought, that perhaps in can be the wheel sensors. The vehicle has been driven only about 3000 miles per year in the spring, summer and fall. It has not been driven in the Spokane, Wa winters. I am taking it to the private MB mechanic who thinks it is the Overvoltage relay. I am also thinking of getting the braking system flushed and wheel sensors replaced, due to the age of the vehicle. Any thoughts or suggestions from your experiences would be appreciated. I also found an article on the AutoInc site. It was titled: Mercedes'ASR II System Can Frustrate Technicians.It stated that ASR I & II had no self-diagnostic capability. The article dealt with a 1992 500SL. After all other options were checked and found ok; the final conclusion was that the Overvoltage was the culprit. The overvoltage relay was replaced and problem was fixed. The Overvoltage was draining 3 times the normal amps. Thanks, Tasha 2 Spokane,Wa
ASR . malfunctioning on 1991 Mercedes-Benz 500SL
by tasha2 in Spokane, WA on April 06, 2011
ANSWER by Superbob on April 06, 2011
Good job finding that one! I recommend replacing the brake fluid as a matter of routine maintenance every 2 years, but I'd let the wheel speed sensors be unless there's a specific problem with them.