Alright. i've got something odd going on. I was making a long trip the other day, with passengers, no less, when every gauge on the dashboard went to zero. (Except the clock) - fuel, OP, temp, speedo, and tach all were unresponsive. They stayed that way for the rest of my run to the airport (and back home). When I got home and started checking, the multifunction relay (black box in the fuse box, containing three individual relays) was buzzing and vibrating... one of the three was oscillating as fast as it could, and presumably had been for hours.

So here's my complete list of observations. Any other suggestions besides "the relay needs replacing" or should I just say "it's fried" and replace it?

1) When the relay is buzzing, everything seems to work normally anyway.

2) It's definitely the turn signal components that are malfunctioning. When I signal a turn, left OR right, the buzzing stops and the relay functions normally. As soon as I cancel the signal, the buzz returns.

2b) The lights are NOT visibly glowing while the buzzing is occurring. They may be oscillating so fast I can't see the glow, but if they are doing anything, I can't prove it.

3) Removing the #7 fuse to the turn signals also stops the buzzing.

4) I HAVE observed instruments functioning simultaneous with the buzzing sound, but it's been rare.

5) When the instruments are not registering anything, the row of warning lights (low oil, low coolant, etc) ALSO refuses to glow, even during the self-test with the switch on but the engine stopped.

6) SOMETIMES, I can remove fuse 7, and then reinstall it. When I do so (while the thing is on and buzzing) the buzzing stops. The instruments are working. Then, I'll drive down the driveway, flipping signals on and off, and very frequently (sometimes it takes longer than others) as I trigger a signal, the gauges will drop and when i get out I discover the relay buzzing again.

So... what's my trouble? Is the relay fried? Or is there a problem in the turn signals themselves causing that oscillation instead of a problem with the relay itself?

That relay has NOTHING to do with the instrument cluster that I can determine. So why are the gauges all dying?

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~Michael S.~
Past cars:

1986 300SDL
1987 300SDL
1982 240D
1982 300SD


Current:

1987 300SDL