Replacing front door, wiring issue. - PeachParts Mercedes-Benz Forum

cmac2012 · #1 06-27-2022, 01:46 AM

My drivers door was bent back severely enough to damage it during a theft a couple of years back. A lot of the paint was chipped off of the frame where the bozo had used a crowbar to make it easier to work the stiff wire they used. I know about the wire because they left it in a big ball in the driveway. It’s that stuff that’s used to hold scaffolding to buildings.

It’s hard to close it completely. You have to slam it like hell and sometimes it won’t close even then. It will latch, but it’s the halfway latch, it’s half loose and won’t lock.

Anyway, I found one on an SEL at a boneyard without a mark on it, opens and closes flawlessly.

There is one bundle of wires I can’t figure out how to detach. I can’t even see it, it’s behind sheet metal. The video shows it, it has a kind of thick braid, you can see it through a small window opening but I can’t see where it’s fastened or how to unhook it when I do find it.

https://youtube.com/shorts/yCytmjMwIYQ?feature=share

Alec300SD · #2 06-27-2022, 03:53 PM

The harness with the braided cover is the power feed for the electric window motor.
They attach to the junction block at the bottom of the door.

Unscrew the Philips head screws at the junction block to free the green and black wires of the harness.

cmac2012 · #3 06-28-2022, 06:16 AM

I have a pretty good idea of where the wire terminates. You can see in the video the movement through that small port. There are other openings along the bottom of the door and I can’t feel any movement of that wire through probing around inside.

So you’re saying that some screws on the underside of the door body at about that point are what need to be unscrewed?

I had a thought today, the existing door is going to be scrap metal as soon as I can arrange it. I’m thinking to cut out more viewports at the approximate area in question. I could experiment on the scrap metal door. Might be a bit much, but I’d rather not take out the regulator, the whole works. Working on windows is one of my least favorite chores. It’s in my future, both of my cars have windows that don’t work.

Alec300SD · #4 06-28-2022, 06:37 PM

The screws that need to be removed are at the wire termination.

IIRC there is also a reusable MB zip tie that secures the harness to the interior of the door.
(Or the harness may route through a narrow path)
A flashlight and inspection mirror can help to visualize the harness routing.

cmac2012 · #5 06-29-2022, 12:13 AM

Yeah, I should’ve had my inspection mirror out already. Good call.

There is a hold down thing, not exactly a zip tie, sort of a C shape with two knobby pieces that pop into holes.

cmac2012 · #6 08-08-2022, 01:21 AM

OMG this is sort of a bee-awch. There are two wires running up to the handle area. I can’t figure what they could before. The locking is done with the vacuum of course. All I can figure is that maybe when the key is turned to lock or unlock it sends an electric signal to the locking system for all of the doors to follow suit.

There are two places where I can’t reach in to facilitate movement/detachment of the wires. As the existing door is going to be in the scrap metal bin as soon as I can arrange it, I cut a couple of viewing windows on the inside of the door:

cmac2012 · #7 08-08-2022, 01:26 AM

The two wires in thick black rubber are the ones that head up to the lock area. The vacuum hose I was able to remove with my hand up in the door. Putting it back in the new door will be a bit of a trick, but I think I can do it.

There is also a wire attached to the rear view side mirror. Again, I’m not sure what electricity does up there - A small heater for the mirror perhaps.

The four connectors for the power seat switch will be relatively easy to do.

I’m thinking I might identify the two wires that go to the power window jack and just solder those at the door. Ideally, if I then attach the vacuum line and the four power seat jacks, I might be good to go.

cmac2012 · #8 08-08-2022, 01:59 AM

Here is where one of the small bundles attaches. I tried to pull the jack out, no luck, not sure I’m going to force it.

I’m thinking I can find the wires that hook to the power window terminal, that little terminal in the door, I can solder those and be OK.

Alec300SD · #9 08-08-2022, 02:51 AM

I believe the 3 wires by the lock are for the burglary alarm system.
It looks like the assembly is covered by a metal shield that is attached to the interior of the door by 3 small (8mm??) screws.

Removing the screws may release the assembly, allowing you to lower it to be able to disconnect the plug.
There maybe a hidden tab or catch that is just not visible right now.

The exterior mirrors do have wire harnesses for their heaters.

cmac2012 · #10 08-08-2022, 03:29 PM

I’m wondering if I can forgo some of these items. The wire harness for the power seats with the four little plugs comes out of the door nicely. It’s a tight fit, but it can be done without using magic.

The other harness on the new door is the one that concerns me. I cannot get it out of the door, and I don’t really want to cut sheet metal away to do it. Here are two photos of it, the second one is what you can see down in the front lower corner of the door. Don’t know how I’m gonna fish that out and get the bundle on the car back in. I am thinking to perhaps use a continuity tester to make sure which wires are which, no guarantee the colors are still the same, there are some differences between the new door and my old one. The motor looks different, it’s in a different location slightly.

I’m thinking it would be easier to solder the wires that I want to use: two wires for the window motor, three wires for the little lights at the bottom of the trim, and whatever wire is needed for heating the mirror, not sure if that actually works, but who knows. The burglar alarm stuff I can leave off.

The small two screw terminal to the left in the second photo is for the window motor, pretty sure, not sure if those two wires come out of that braided harness bundle.

INSIDIOUS · #11 08-08-2022, 05:58 PM

About your window motors. I think I have seen different regulator systems with different gear counts ( maybe they call it Z factor) even in the same model and perhaps even year, but do commonly vary front / rear and among models. hardly matters unless you are going to replace the motors you have to match it to the new one. (of course R/L - D/P matters)

As long as you have the door apart take off the motor now and take notes so you can purchase the correct one when the time comes without having to open it first and drive around with the door card off and window in UP, inOP and propped until you find a great deal on a replacement. Don't ask me how I know. I'd even photograph it for future reference. After several models/years you lose place.

cmac2012 · #12 08-08-2022, 06:07 PM

OK, let’s switch back to civil mode. I have no idea if the new door will not perform well in the raising and lowering of the window. I suspect it will, as the SEL I took it from was in really good shape, hardly a mark on the body, and the front door closed and opened flawlessly. I only mention that because I’m not sure the wiring color code will be identical. The SEL was a 1990 model, my car an ‘86.

I’ll carefully do a continuity test to make sure I’m soldering the right wires. It looks to me that I can get away with only soldering five or six wires which will be a lot easier I think than trying to route that cable in and out. Mercedes definitely did not make this an easily serviceable item. The power seat switch wiring is easily serviceable, the other bundle absolutely not.