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Old 06-15-2015, 05:23 PM
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1987 300D electrical issue - door open sunroof operation, fuse 9

I was closing my sunroof last night with the key out and the driver's door open. It stopped half way, so I inserted the key and turned it to run and closed it the rest of the way. I didn't think much of it until I jumped in the car this morning and the radio did not turn on. I then noticed the clock was stuck at 8:18 -- the exact time I closed the sunroof.

I started piecing things back together in my mind. Checking the fuses showed #9 was blown. This is not supposed to power the sunroof to my knowledge? Windows, sunroof, radio, etc have always worked with the door open (but moved slower). #9 fuse looked brand new, while the other fuses looked original (or close to it). This leads me to conclude this was a recurring problem for the previous owner.

I read something about a diode that blows causing voltage to leak from the door open fuse to other systems causing electrical gremlins. It was on a 190D, though (Seat Diode - Mercedes-Benz Forum)

Any ideas where to start?

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Garage:

2005 Volvo S40 T5 AWD, 77k
1998 Saturn SL2, 244k - 35 mpg (gone, never forgotten)
1987 Mercedes-Benz 300D turbodiesel, 4 sp auto, 156k - 28.7 mpg
1993 Tracker 4x4, 2 door, 8v, 3 sp auto. 134k - 25 mpg
1996 Tracker 4x4, 2 door, 16v, 3 sp auto. 110k - 28.6 mpg

WARNING: this post contains thoughts that may be discovered by the state of California to cause cancer.
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  #2  
Old 06-15-2015, 05:32 PM
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The place to start is the wiring diagram in the fsm. There probably is a diode, as there is in a190. But you really need to check the diagrams for verification and location. As to why an unrelated fuse would blow, my speculation is that the sunroof drew power from wherever it could once the primary path across the diode went away. Again, subject to a review of the relevant docs.
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  #3  
Old 06-15-2015, 05:35 PM
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I'll try to find the documents in the FSM.

Thanks!
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RenaissanceMan Labs: where the future is being made today.

Garage:

2005 Volvo S40 T5 AWD, 77k
1998 Saturn SL2, 244k - 35 mpg (gone, never forgotten)
1987 Mercedes-Benz 300D turbodiesel, 4 sp auto, 156k - 28.7 mpg
1993 Tracker 4x4, 2 door, 8v, 3 sp auto. 134k - 25 mpg
1996 Tracker 4x4, 2 door, 16v, 3 sp auto. 110k - 28.6 mpg

WARNING: this post contains thoughts that may be discovered by the state of California to cause cancer.
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  #4  
Old 06-15-2015, 05:44 PM
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An interesting problem. I got to know the electrical system of the 1987 300D very well due to various boogerings compliments of the PO. One thing is that the windows and sunroof are supposed to operate only with the key ON. It sounds like someone has moved that wiring to the power seats, which are designed to work with the key OFF and the front door(s) open. (That's where the diode is, BTW.)

You need to explore the wiring of you car and compare it to the FSM diagrams. The "seat diode" is at the rear of the fuse/relay box.

Jeremy

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