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Wagon Rear Hatch Wiper Wiring Issue

3K views 7 replies 6 participants last post by  4Matic 300TE 
#1 ·
Here is the weird thing about the the rear wiper for the hatch is that it will work when I lift the hatch halfway up, not when closed. All the way up, it will stop working like there is some wire break. Can it be possible that a wire has gone bad? I thought the wiring is multi-strand? Don't think the relay is the problem.

Is there a wiring diagram for the hatch electricals that I can locate on the web?

I have other strange intermittent switch issue with the rear interior lights. They sometimes don't work to manually have the lights on when switched. Likely not related and separate issue.Does what when hatch or rear doors are opened though.

Thanks for your thoughts!

Rod
 
#2 · (Edited)
the wiring diagram for the stuff in the wagon hatch is spread across a bunch of drawings.

central locking:
http://new.freescruz.com/.priv/W124/w124CD1/Program/ETM/2480300.pdf

exterior lighting (3rd brake light + license lights are in hatch)
http://new.freescruz.com/.priv/W124/w124CD1/Program/ETM/24821300.pdf

tailgate closing assist:
http://new.freescruz.com/.priv/W124/w124CD1/Program/ETM/2472200.pdf

wipers (including rear wiper)
http://new.freescruz.com/.priv/W124/w124CD1/Program/ETM/24821200.pdf


in most of these drawings, stuff thats in a dotted box U22 is specific to wagons...

note that X8 across all these various drawings is the tailgate connector strip. this is near the left hinge behind the interior trim above the left rear side window, and is where all the wires terminate. the tailgate harness has terminals that are screwed down to this strip, this harness is 1245403707, and its much better to replace the whole thing if you've identified a prroblem, rather than try and hack it.

OH, your problem could be as simple as a loose connection at said terminal strip... this terminal strip looks something like this...

 
#4 ·
With the age of our 124s, broken wires at hinge points is relatively common. The engineers route the harness to minimize outright bending but some does occur and with it comes work hardening of the copper strands. The problem seems to affect rear doors first, even though they are typically opened less frequently than the front doors. My recently-totalled 88 300TE had only 1 remaining functioning window (the front RH) and fixing the inop windows was going to be a winter project. No more.

Of course the same issue can and does affect the hefty bunch of wires going into each side of the liftgate. I wish I had a vintage video showing how assembly line workers threaded those harnesses into the assembled and painted bodies. I'd pay moy money to see such a video. Anyway, on my aforementioned TE the first liftgate hinge item to be affected was the washer hose so using the washers would cause blue fluid to run out the bottom of the liftgate. Then it was the RH license plate bulb.

The broken wiring problem affects just about all cars sooner or later and our 124s last longer than most. I recently worked on a mid-2000s VW Jetta or Passat with inop window on the driver's door. A bunch of wires were broken in the boot/bellow/gaiter area. For that car VW released a revised design door wiring harness to fix the problem. Side note: on that particular car you access the door guts by removing about 30 screws and then the door *outer* panel. Weird.

Automotive Trivia Question: anyone know what mid-60s American car used that same technology?
 
#7 ·
It will be a broken or fractured wire in the left hand hinge rubber. I guarantee it (well almost!).

Very easy to check. Put your multimeter in continuity buzz mode (diode check). Remove the rear headlining panel to access the curved multi connector and check the connection to the wiper (all wires) while raising and lowering the tailgate.

Job done, Problem located!
 
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