[Resolved] Dead Sunroof Relay (124)

Discussion in 'Electronics' started by chilsta, Jul 12, 2016.

  1. chilsta

    chilsta Hardcore MB Enthusiast

    Jul 18, 2010
    '94 S124 E300D
    A few months ago I went to close my sunroof and nothing happened. During later investigation there was no blown fuse & I could hear clicking in the back by the motor.
    I closed the roof manually and it closed easily enough so I was fairly sure I could rule out a mechanical fault.

    I looked around online and the consensus seemed to be that it was a relay issue, but couldn't find any further than that, so thought I'd add this post in case it helps others with the same issue.

    I removed the relay from the bottom of the motor and found this inside (the case pops open with the twist of a flat screwdriver):



    Inside the case was a load of black and rusty dust. Things didn't look good as far as the relay was concerned, but the signs were good that I'd found the problem. I cleaned it up a bit, including the relay's switch contacts, and tested that the contacts had continuity across the plugging pins, but still no roof movement.

    I tried to arrange with a friend to borrow the relay from his 124 with a working roof to see if that resolved my problem and prove the fault, but he's some distance away and either he, his car or I were unavailable. Then a relay popped up on ebay for a tenner so I took a punt.
    The relay did indeed solve the problem. Good result- about the easiest thing it could have been. Some roof problems sound like a nightmare to resolve.

    Now that I know the old relay was at fault I'm going to try reflowing the solder on the board and see if I can get the old one revived as a spare. The relay was clicking with the switch in both positions and I'm fairly sure the contact continuity is OK, so it points to a fault in the relay coils energizing circuits. Will update here if I get an answer.

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