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  #31  
Old 10-06-2013, 05:51 PM
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Originally Posted by Graham View Post
So what is there in a rear door that would cause fuse 1 circuit to short? Perhaps the window switches have a light and the harness to the door is chafing?

How did you fix the problem?
The blue wire from the window switch in the door panel ends up in pin 12 of the instrument cluster. I looked inside the accordion looking rubber between the door and the frame but didnt see anything obviously wrong there. Next move is to remove the driver seat, rear door panel, carpet and center console to remove the harness which i dont have time to do yet. Right now i disabled the rear window from the switch by pulling the plug at the center console.
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  #32  
Old 10-06-2013, 06:51 PM
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Originally Posted by cooljjay View Post
Have you ever removed the bundles of ground wires behind the cluster and cleaned them?

Its important to clean all the ground contacts in the car as normal maintenance.....there are two in the trunk, one near the gear shifter, bundles behind the cluster, one near the passenger headlight, ground strap and battery to chassis ground......dirty grounds can cause all sorts of issues....
My problem, is one too many grounds
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85 300D14 GLK250,72 350SL, 98 E320
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  #33  
Old 10-06-2013, 07:13 PM
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Originally Posted by my123ca View Post
The blue wire from the window switch in the door panel ends up in pin 12 of the instrument cluster. I looked inside the accordion looking rubber between the door and the frame but didnt see anything obviously wrong there. Next move is to remove the driver seat, rear door panel, carpet and center console to remove the harness which i dont have time to do yet. Right now i disabled the rear window from the switch by pulling the plug at the center console.
I have the door apart and the plastic cover on the door pillar removed. The switch on the door is disconnected.

The wiring to the door runs through a strong reinforced black sheath. I checked from door window switch through the concertina and down the pillar to the floor and there is no damage to the wire sheath and it is not grounding anywhere that I could see.

I also checked for a ground from the blue switch wire (socket 5) using both socket 4 (brown) and the door itself. No ground with door open or closed!

So why do we get a short when the door opens? The only other thing that changes, is the door switch. It has separate wiring and seems to operate the courtesy light properly.

I wish I had looked for the short when I had the car interior totally stripped a month or so ago!

My next step will be to see if I can find where the blue wire to that door connects to the main switch and disconnect it. Diagram shows it comes right out of the console window switch socket 5.
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85 300D14 GLK250,72 350SL, 98 E320
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  #34  
Old 10-06-2013, 09:34 PM
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OK I found the problem.

Only thing that made sense, was that the wiring in the door pillar was shorting. I set up my meter so it plugged into blue/brown sockets of window switch. Then tried jiggling the 4-wire harness is sections. I finally found that jiggling the section inside the pillar caused a short.

I opened up the woven covering down at the base of the pillar and cut the blue wire. I had in mind to pull it out and run a new separate wire. When I pulled from the switch end, I got a piece about 12" long. And other end had not moved! Pulled it the other way and it was clear it had been broken inside sheath for some time.

I then cut all the wires at the pillar base and pulled the harness out from switch end. All but one wire were mangled. Yet the outside sheath showed no sign of this! I don't know what did that to the wires inside the pillar. Only things I know of in there are the door lightswitch and the bracket for the door check. I will have a look with borescope, although the one I have is not too good in tight places.

I may run new wires or perhaps just splice the existing. But I need a better sheath. Maybe use some heat shrink? I need something that can be fed in and make some tight turns - Probably why they used the woven type.
Attached Thumbnails
w123 300d - no climate control lights-123-window-harness-cut.jpg   w123 300d - no climate control lights-123-window-broken-wires.jpg  
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  #35  
Old 10-07-2013, 09:12 PM
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Thats great! You just saved me some troubleshooting time. Could it be that the seat belt mechanism had something to do with it? Im thinking run the 4 wires inside a viton hose.
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  #36  
Old 10-07-2013, 10:13 PM
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Originally Posted by my123ca View Post
Thats great! You just saved me some troubleshooting time. Could it be that the seat belt mechanism had something to do with it? Im thinking run the 4 wires inside a viton hose.
I just got it all back together.

I could not see much up inside of pillar, but I could feel some sharp edges. Perhaps back of welds for doorcheck bracket. But not sure.

What I did, was run a new 3 conductor wire plus a single separate wire for the ground (brown)- that way the live wires can't come into contact with the ground wire. The 3-conductor wire has a PVC jacket which is much better than that mesh cover the car originally had. The mesh really provides no protection. I put disconnects up near the door switch. This will hopefully make it easier to take door off next summer for some rust repair on seal channel.

I tested the dash lights a few minutes ago after I closed everything back up. They stay on regardless of which door I open!

Seems to me, that that short in door is what destroyed the traces on the cluster circuit board.
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Last edited by Graham; 10-08-2013 at 11:45 AM.
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