One morning recently, my battery was too weak to start Olga (a 240 DL wagon). I popped the hood and heard a buzz coming frome what I learned later was the Frequency Valve. The keys were in my hand, so I figured that is what had drained the battery.

There's a relay on the fender wall behind the coil from which I unplugged the connector, and the buzzing stopped, so I took off the relay and tested the terminals. The coil terminals read continuous, but the hot terminal (30) through to the output terminals also read continuous on both outputs (87 and 87a).

So I opened it up and tested with the switch in both the opened and closed position. Both positions resulted in continuity. This doesn't sound like any kind of relay I've ever seen, and nothing looked wrong with the guts of the thing ... but wait! Looking into the relay cover, I found a small strip of fabric. I took this strip and stuck it between the contacts that were closed in the relay's "relaxed" position and buckled the relay back up.

Plugged the relay back into the car and there was no buzz, so I got in and started her up. She's been running smoothly ever since.