The driver's side rear window on my 95 E320 cabriolet will go up, but it won't go down. Here's what I've done so far:

- I put 12v directly to the window motor. The motor works fine up and down; window goes up and down. No problem with the motor.
- I inspected both switches - front console and rear seat. The window goes up but not down with each switch. I took the switches apart - they look clean.
- The window goes up with all the others when I operate the cabriolet top. It will not go down.

This problem came all of a sudden. It didn't get flaky (intermittent) and then quit. I simply stopped working altogether. What else can I check? I'm beginning to think one of the relays is bad in the convenience control module.

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95 E320 Cabriolet, 159K