In the past we have had severe AM radio interference in our M-Classes. One of the preferred stations is a quality one about 100 miles from our home which puts us in a fringe reception area susceptible to interference. Other vehicles parked next to the ML did not have the interference, however, including our 1978 300SD. Our 1998 ML had the radio replaced and extensive diagnosis at the dealer with little improvement. The tech at the dealer said it sounded like a grounding problem. When we bought the 2000 ML320 we had the same problem and again the dealer did a lot of work trying to find the problem, including a new antenna amplifier in the cargo door and cleaning up all the connections in the door. None of it helped much. The interference was especially pronounced when accelerating or using power options like the windows or outside mirrors.

I have found what has worked the best and have delayed posting this until I had time to use the vehicle and verify the fix will last. Lately we replaced the battery in the 320. The negative cable is grounded to the chassis at a bolt on the firewall. There are two other wires attached to the bolt also. I removed the nut and cables from the grounding bolt, used jumper wires to maintain electrical connections, and burnished the bolt, contact side of the nut, and wire connectors. They were then coated with electrical conductivity grease and reinstalled. The result is that the radio is working at a very acceptable level now. It appears grounding was the problem and the fix was easy.

There is a service notice sent to dealers about this problem and a resource from another forum is going to send me a copy this coming week. I will pass it on.

By the way, your post was earlier this month, have you done anything about the problem since?

Jim W.