TD tailgate light switch - PeachParts Mercedes-Benz Forum

dcraigk · #1 05-31-2020, 07:47 PM

Anyone know where and what the switch looks like in the tailgate that makes the rear interior light come on? My rear interior light won’t come on.

I tested the door switches to the light and they are ok. I looked at the schematic and I see the door switch ground wire and tailgate ground come together at a terminal under the rear panel between the speakers. I removed the panel and disconnected the ground going to the tailgate switch and now the light comes on when I open the rear doors. So whatever is supposed to trigger the ground when the tailgate is opened isn’t working.

I just installed a new tailgate latch from MB thinking that would fix the issue but it didn’t.

resto108 · #2 06-01-2020, 12:50 PM

I just went through this last week! So on my 82, only the cargo light switch on the center console and the actual switch on the dome light itself would turn on the rear dome light. I lived with it for years, but finally dug into it.
The first thing I found was that it wasn't wired per the 82 wiring diagram. I couldn't find the courtesy lighting part of the 81 wiring diagram. The cargo light switch isn't even on the diagram. The light itself does not have three positions, either. So to get mine to work "correctly", I switched the two wires in the two wire connector plug, then cut the one coming from the cargo light switch and ran a new wire to ground. So now, when you open the hatch or the two rear doors, it comes on. When you turn the switch on the light to always on, it comes on. The only thing that doesn't work is the cargo light switch up front. Since its not on the diagram, I didn't know how its interconnected, and its the least feature I would use, so it got cut. I'm not sure how you could make all those functions work with just two ground wires, though.
The second thing I found was the tailgate latch switch was always open on my car. I had another latch, so I swapped it out. Didn't really see a way to change just the switch. Take the two wire connector off the latch and jumper the two pins and your light should come on.

dennislarock · #3 06-01-2020, 07:53 PM

Does it work from here?

dcraigk · #4 06-01-2020, 08:02 PM

Yes

dennislarock · #5 06-01-2020, 09:05 PM

Mine work correctly (both '85TD & '83TD). I have to dick around with the '85 washer nozzle later this week. I have the panels off... I'll take some pics of the wiring ...if you think that may be of help.

dcraigk · #6 06-01-2020, 09:14 PM

I’m trying to figure out what triggers the ground wire so the light comes on. The wire between the hatch and the body may be severed. I need to check continuity but I’m not sure that’s it.

The wiring schematic looks like the connection may go through the wiper motor

dennislarock · #7 06-02-2020, 12:00 AM

OK... I'll trace, test, confirm ...and, get some pics thurs/fri (sooner, if the wife lets me).

dennis

shadetreemechan · #8 06-02-2020, 06:48 AM

The actual switch for the light is on the tailgate lock mechanism on the passenger side.

vwnate1 · #9 06-02-2020, 11:10 PM

Don't forget : M-B just released a slightly improved version of this latch and it's under $150 from you dealer is he's honest .

I went through all this to get the broken inside handle replaced and working again, save the details of how to get the latch out, it's like a 1950's "Chinese puzzle", once you get it just so it comes right out .

dcraigk · #10 06-02-2020, 11:11 PM

I bought a new latch from Keyes. Less than $100.

I hoped it would fix my light problem but it didn’t.