Open Doors turn on Radio & more W124 300E

[d2bernhard]

1986 w124 300E 211k miles

Initial problem was dead light in Glove Box. Bulb was good. I used the contacts from the visor to test for hot and ground and managed to short them blowing fuse #9. Replaced fuse and all works well (except glove box light still, I believe the ground is bad) but a lot of things now work as if the key is in position 1 when the doors are open. As a matter of fact, everything I think.

So, no key in ignition, Doors Open:
Seats (normal I know)
Radio
Cigar Lighter
Windows
Rear Defrost
Wipers
SRS test lamp illuminates for normal duration

What is wrong? Where do I start?

Thanks! David

[Cliff_W140]

I had the same problem with my old 420SEL. I actually enjoyed the malfunction, but it ceased to work after a couple weeks. I realize waiting for it to fix itself does not appeal to many, but the problem eventually went away with no noticeable consequences.

[speedy300Dturbo]

The power seat diode has gone bad. It's a small two-pin thing in the back of the fusebox. It's called a "contact bridge" in most online parts catalogs.

[d2bernhard]

Thanks SpeedyD!

I believe I have got it out. Someone has been here before with this car and conveniently left it cable tied outside the fuse box for easy access. I opened it and it looks fine inside. Car still acting the same with this removed, which brings on a couple more questions:
1) Is there more than one of these? (Need to make sure I got the right one since mine was not in the original location in car.)
2) If fried, are symptoms same as if removed? (Mine is now out and car is acting same.)

Thanks!

I performed the diode test using my multimeter and it shows a small reading (0.255) exactly the same both directions -- indicating this thing is bad.

[speedy300Dturbo]

Hang on. On your car there are two of these diodes. One of them is zip-tied outside the fusebox in the vicinity of the brake master cylinder, and another one is actually in the rear of the fusebox. To get to the latter (which is the culprit in your case) you'll need to open the fusebox and remove all the visible screws so the back cover can come up.

[d2bernhard]

Thanks! So then, what does this other one do and don't my MMeter readings indicate it is bad as well?

[speedy300Dturbo]

Originally Posted by d2bernhard

Thanks! So then, what does this other one do and don't my MMeter readings indicate it is bad as well?

I don't know, but this thread covers the function of that resistor in great detail:

http://www.peachparts.com/shopforum/showthread.php?t=32224

[d2bernhard]

Ahah, I've seen that thread. Plot thickener added by SpeedyD to enhance thread flavor and robustability.

I found the diode and it is fried. Will get a new one. Car seems to operate normaly without it. Hmmm?

[d2bernhard]

Diode installed, all is fine