Gene, What I was saying was that you could have accessed your wiring plug without removing all that molding.
Ah! With the latest pictures now I understand what you were talking about. You are completely correct. If the wiring harness is mounted far back it is easier to access the plug by removing the bumper.
I connected all wires, plugged in 25A fuse in F18 in the fuse box, and hooked up my trailer.. But the lights DID NOT WORK! I checked the terminal with a tester, and learned that there is no 12VDC.
You checked between the thick red wire and the thick brown one? Try between red and some other ground. Also are you testing with the relay not hooked in? You won't see a voltage difference above a tenth of a volt or so if the relay box is connected. Try another fuse. If you had to cut the wire check that your solder didn't break.
Grey Unknown
Pink Right Blinker
Yellow Unknown
Orange Brake
Green Left Blinker
Blue Running
The Grey is the Backup light. The Blue changes to White after one of the wiring harness plugs so if you can't find Blue look for White. one more thing, F12 = Runniging lights, F15 = Brake lights F2 & F25 are the Turn Signal fuses in addition to the constant 12V fuse F18. Any of these fuses could cause things to not work. F18 is used to power the Mercedes isolation circuit to run the trailer lights. I don't think you need this if you are using a non isolated after market trailer lighting adaptor.
Mike
Vehicle: 2005 C320 4matic, 2005 ML500 Special Edition
Location: Bayarea
Posts: 56
Thanks for advises, Gene and Mike. I was finally able to get 12VDC and signal voltage to the plug.
The bottom line was that my dumminess was beyond imagination of both of you I was looking at a wrong fuse box (the one in the front passenger seat's leg space). Coincidentally, F18 was open in that fuse box, so I plugged in my fuse there and was spinning. I found the right fuse box under the hood after reading Mike's comment and got skeptical if I was looking at the right fuse box. I must confess that this was the first time I worked on my ML..
Gene, I hooked up modulite 18187 to the plug as seen in attached pic. I can't test with my trailer now, but I did confirm with a tester that the red wire and other signal wires got 12DCV voltage. Please let me know if you foresee any problems.
Other than wires shorting out? <g> Be sure and seal those wires well. I would consider smearing some of that "liquid electrical tape" gunk over the connections.
Vehicle: 2005 C320 4matic, 2005 ML500 Special Edition
Location: Bayarea
Posts: 56
Thanks again Gene and Mike.
One last question. Currently, the 4-pin flat plug from modulite is hanging around near the hitch on my ML. This works for now, but probably is not a good idea in the rainy season. Ideally, I'd like to have a 7-pin round plug with waterproof lid like the OEM one . I went to Uhaul, and found adapters and a little piece of metal to attach the adapter to somewhere on the bumper, but there are no convenient screw holes on the bumper as seen in this doc (page 4).
I was looking at a wrong fuse box (the one in the front passenger seat's leg space). Coincidentally, F18 was open in that fuse box, so I plugged in my fuse there and was spinning. I found the right fuse box under the hood after reading Mike's comment and got skeptical if I was looking at the right fuse box. I must confess that this was the first time I worked on my ML..
Linear Mode
