When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Ok, I have read almost all the threads on trailer problem, but have not found one that has my symptoms.
I installed an oem trailer hitch with oem wiring, plugged into rear SAM, hooked red wire to fuse box at brown location, and brown wire to ground. I do not have a brake controller so I did not use the green connector. I did have the dealer reprogram the Sam.
now for the problem, I only get running lights, no blinkers, brake, flashers, just running lights. Thought it might be the led issue so i bought the special led 7 to 4 adapter, with this adapter I get nothing.
checked ground, check for power at connector, I am about to for go the oem wiring and tap into vehicle lighting, but before I do this I wanted to give a shout out for help, and I would like to keep the feature of the vehicle knowing a trailer is connected. Added note, in all my troubleshooting the vehicle messages have said nothing about a lights not working, or stopping me from raising the suspension, when I have trailer hooked up, so as far as I can guess the vehicle does not see the trailer.
Brown is universally the color for electrical ground on German vehicles. Red is likewise universally the color for a direct to battery (not switched) positive. Connecting red to brown certainly seems incorrect and likely to achieve a result of nothing. WIS instruction AN31.19-P-8080-03GZA details harness connection ... perhaps the Major will post it.
I connected the red wire to the brown location on he fuse panel. I will check to see if this is power. If k understood correctly this was where the trailer harness was supposed to get power.
I didn't yet google for what Kent posted, but it still sounds like you connected the positive wire to a ground. Or, what do you mean by "brown location"? Do you happen to have a copy of the instructions that you can post?
The fuse box has locations on it for certain added items and the are color coded, purple, red, brown etc.. from my research the brown location was for trailer wireing
I bought hitch used, and the just cut the red wire with the cool fuse holder. I install an inline fuse, that is why the wire you see is black, but it is connected to the red wire on the hitch harness.
as for instructions, I have a digital copy of the mercedes shop manual for my gl.
Last edited by Jakehabing; 02-25-2019 at 02:09 PM.
I don't have the fuse chart where I am right now. Do you have yours?
Which "socket" is the hot side? The one you plugged into? Or the one further down the black, plastic "frame"?
Also... maybe I'm just not understanding how this works, but how can you get multiple functions through just one wire? Running lights and brake lights can follow the same wire, but you also have L & R signals.
If I understand it correctly this is where battery power goes to the trailer, the turn signals and brake lights go through the rear sam. But how the vehicle tell there is a trailer hooked up and then sends power to he certain lights, is the problem I think I am trying to diagnose. And since I did the install myself, I can't blame somebody else😉
I do not think adding the trailer wiring is plug and play to the rear SAM. I think you have to go into Xentry and add the trailer port to the configuration. Do you have access to a DAS/Xentry system?
I do not think adding the trailer wiring is plug and play to the rear SAM. I think you have to go into Xentry and add the trailer port to the configuration. Do you have access to a DAS/Xentry system?
what do you mean by the above statement, I am not familiar with xentry. Is it something I access from the vehicle?
I did have the dealer reprogram my rear sam for the trailer package after I installed the hitch.
If I understand it correctly this is where battery power goes to the trailer, the turn signals and brake lights go through the rear sam. But how the vehicle tell there is a trailer hooked up and then sends power to he certain lights, is the problem I think I am trying to diagnose. And since I did the install myself, I can't blame somebody else😉
Yeah, I don't understand it. If we take the simplest type of trailer hook-up - a flat 4-wire connection - one of them is a ground (white wire), then there is the running light/brake light circuit (brown wire) and then the two turn signal circuits (yellow and green). That's it. There is no separate "power" going to the trailer. Power comes through one of the 3 circuits when it is needed, not all the time. Now... maybe that power wire you hooked up gives power to the "trailer" part of the rear SAM and then the SAM has the individual power wires leaving it? But, back to what I first said... I dunno that part of it
Is the 20amp fuse or the 30amp fuse the trailer. If it's the 20 then I have it plugged into the right location.
According to my fuse chart (check yours to be sure), the 30a is "Trailer Brake" and the 20a is "Trailer Hitch". The lower, 25a is "Rear Fan" - nothing to do with trailers, obviously.
I have phantom power on running lights, and turn lights with now load. As soon as there is a load power is gone. There is enough power for the little lights on the adapter, but once I use test probe then no power. Phantom power is 5.21volts on volt meter.
Could that phantom power be the power the SAM (or whatever) sends out to check each circuit for bad bulbs?
I've never used one of those testers (always just a DMM). Silly question, but do you have the running lights on and the flashers on while you are testing for V?
Just running lights, no flashers. It could be some type of signal from the sam. Here's another development, at the fuse panel I only have constant 12v at the trailer brake location, none at the trailer hitch locations. I plan to call the dealer tomorrow, they said they reprogrammed the rear sam for a trailer, but if they did, why does the vehicle not see a trailer. I have tried different trailers, with leds and with old type lights. I read another post were bajatommy had the same issue I am having, but back in 2014. Tried to PM them on how they fixed it, so far no response. Thanks for everyone help.
the tester is just a lighted probe, I use a dmm as well.
Did you figure out what side of that "brown" location is the load side? In other words, looking at my fuse for example, one side is the hot side and the other side is the load side. I would "assume" that your positive wire that you hooked into there needs to go to the load side?
Well, as always dealer said bring it in and we will look at it. Not sure when I am going to have time to get off work to take it to them, they are an hours drive from me. Does anyone know what the symptoms would be if they actually did not reprogram the sam?
Hey im having exact same issue you're going thru. have you figured it out what was the problem? I have installed a factory hitch and a used sam off ebay my self, and wollaaa NO power to my trailer lights. i assuming sam perhaps did not need to be program due to being used and programmed already. Id be appreciated if you can share your experience..
Hey, so my problem was that the reprogramming Did not take until the 3rd try. One way to find out if your Sam is programmed, is to hook up a trailer, plug everything in, then try to raise the suspension. If it tells you that this option is not available, then your Sam is programmed for a trailer hitch. But if it starts to raise then you need a reprogram. Hope this helps.
Does your trailer have led lights? I had to get a trailer plug with resistors so that the car would recognize the trailer.
It does not - just the regular. Dealer have apperantly programmed the rear sam for trailer lighting, but no luck. Looks like no power goes to trailer lights. Once i feed the lights w/12v, lights comes on. Called dealer, couldnt help but at least they refunded me the money.
Unfortunately, i do not have airmatic suspensions on the car. Just the regular suspensions. Took it back from dealer yesterday, and trailer lights are still not working.
I have the exact problem "Phantom" juice to the trailer lights, glowing But no real power for my Running lights and I cant find the main source for the running light!!?
Any solution to this? Tried a trailer light board no power, tried old trailer with traditional bulbs no power and then tried new trailer with dynamic led lights and I get the indicators swiping fast but no other lights are getting powered. The swiping indicators are always on even without having the indicators on. What is the solution to this???
02-24-2019, 04:37 PM
