Found the pdf for the component locations:

https://www.startekinfo.com/StarTek/outside/12265/disc_2/program/ETM/1982%20300_comp.pdf

Figure 2 on page 8 of the pdf shows terminal block C136.
It has 8 pins and is located at the top of the tailgate frame.

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

I will get into the hatch switch this weekend. It looks like a semi hard job in that the lock mechanism has to be disconnected and removed. The "how to" I read says the wiper motor, support bracket and miscellaneous other parts need to come out first and then the lock with the switch attached. If it's the switch I'm hoping that I will be able to find one. Thanks for the diagrams and advice.

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1985 300TDT
2013 E350 Bluetec

Looking forward to seeing what you come up with.

That electrical connection is under the cover in the back. I saw it when I changed my hatch struts but I didn’t know what to look for.

I have 2 TD’s. The gold one acts like yours. On my black one, closing the hatch makes the light come on and it goes off when I open it. I read somewhere that someone had the same problem and changing the hatch latch fixed the problem.

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1985 300CD, CA
172 Anthrazitgrau/Palomino 154

1985 300TD, CA
040 Schwarz/Palomino 154/3rd row seat

1985 300TD, CA
473 Champagner/Palomino 154/Cargo cover

I'm hoping it is the hatch switch that has gone bad because both rear door switches work {I swapped them to the front to test}. I'm going to be delayed in looking at it because I don't want to dismantle the lock mechanism without having a new switch to replace it....don't want to take it apart twice and I am using the car while trying to bring it back to life. I had an 85 Champagne 300TD like yours. Sold it a year ago with 387,000 miles and regretted it ever since. It was a one owner car and always garaged and maintained by MB. Ran beautifully and still didn't burn a drop of oil between changes. Just got this 85 Barolo Red car a few weeks ago. One owner car but has been neglected for the past several years. Original owner passed and the car was parked outside and left to deteriorate under the southern sun. Long process of trying to bring it back to former glory.

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1985 300TDT
2013 E350 Bluetec

Wiper motor and bracket can stay in place. Once lock mechanism is unbolted it must be rotated 90 degrees and will only come out toward the passenger side down toward the bottom of the door. You can try all day to get it out in the direction of the drivers side and it wont work.
The lock must be positioned so that the latch counterweight is pointed toward the outer skin of the door.



I have done it now enough that I can do it in a couple minutes, but the first couple of times it took forever.

The switch can be taken apart and the contacts cleaned if it is not physically broken. I have never seen a switch physically broken in situ, but have broken one trying to get it out without removing the lock mechanism first.

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1985 300 TD 448K
1984 300 TD 278K

1983 240D euro 240k
1994 f-250 idi turbo 330K
1986 f-350 IDI
1987 F-350 IDI

1985 JD 1050 4wd
1965 IH 3660

Good to know the switch might be serviceable with contact cleaning. I have had to put this project on hold for about a week. My house is being tented for termites tomorrow morning...welcome to Florida

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1985 300TDT
2013 E350 Bluetec

I replaced the lock mechanism a few weeks ago with a new one from Mercedes. No change, the light will only come on with the dash switch.

I thought I'd try again today since I'm stuck at home.

I've got continuity at both rear door switches, so they're good. I also have continuity from the drivers side switch to the light. The passenger switch is wired from the drivers side. I also have continuity from the grounding location by the passenger tail light to the drivers side rear switch. Everything check out, but I still can't get the light to come on.

What I can't figure out is the wiring to the light itself. There are 3 wires. Red w/ white stripe (+) that goes to one side of the bulb, brown w/ white stripe that goes to the other side of the bulb. This must be from the dash switch. Then in the middle is a brown w/ gray stripe. This wire goes to the door switches. I have continuity to the drivers side rear door switch. I just don't see a path for that wire to contact the bulb and complete the circuit.

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1985 300CD, CA
172 Anthrazitgrau/Palomino 154

1985 300TD, CA
040 Schwarz/Palomino 154/3rd row seat

1985 300TD, CA
473 Champagner/Palomino 154/Cargo cover

I'm not familiar with the wiring for the rear dome light so can't add anything for you. I still haven't solved my issue either....car has been on the back burner with everything going on. Someone here will chime in on the wiring details.

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1985 300TDT
2013 E350 Bluetec

I removed the tailgate ground wire at the terminal block so only my door switches control the light. Now the rear interior light comes on when the rear doors are opened. Now I need to find the switch that is activated when the tailgate is opened.

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1985 300CD, CA
172 Anthrazitgrau/Palomino 154

1985 300TD, CA
040 Schwarz/Palomino 154/3rd row seat

1985 300TD, CA
473 Champagner/Palomino 154/Cargo cover

So for the wiring, you have the colors and functions right. The path is as I said in my other reply. Maybe an electrical engineer can enlighten me here, but when you have a light assy with one power wire and two grounds, mounted in a papier mache panel, I don't see how you can control it three different ways.
1 being cargo light switch that is independent of whether the doors or tailgate are open
2 being either rear door or tailgate
3 being the switch on the light assy itself.

Did you look at the schematics from other years? I think my 85 is like the schematic.

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1985 300CD, CA
172 Anthrazitgrau/Palomino 154

1985 300TD, CA
040 Schwarz/Palomino 154/3rd row seat

1985 300TD, CA
473 Champagner/Palomino 154/Cargo cover