m1kefries

I have a 2007 ML320 CDI that the dealer installed the trailer hitch on. I've had a problem with the dash indicator for the trailer lights from day one. It started when I had a trailer hooked up and it would tell me that one or more of the lights were out. When I checked the trailer the lights are fine.

I've had it back to service several time and gotten various answers from, LED trailer lights don't draw enough current to the latest TSB for the welding of the hitch was causing the wires to come loose.

Now I am getting these same warning lights when I don't even have a trailer connected...... Of course I think it is the PAM module in the back that is screwed up, but I just wanted to know if anyone else is having the same or similar issues?

nick bben

Hi Mike
We have had an ML320cdi for just on 12 months and had hitch and trailer wiring harness installed locally by MB dealer. Were informed by dealer that light emiting diode (led) lights no problem, computer can be programmed to handle them on trailers. Also fitted brake controller. Symptoms were warning messages in dash for rear brake lamp not working, tail lamp not working. After many months of trying options, eventuallly getting the computer black box re-programmed in Germany and air lifted back to Australia, it was no different. In the end the dealer fitted a series of resistors into the lines feeding the trailer to trick the system. It still isn't perfect, as the trailer might not be hooked up at the plug correctly and there is no warning that the indicators aren't working as happened yesterday in traffic, another driver let me know at traffic lights. Initially we were told it was the brake controller. There is I am told an after market system to fool the computer. As there is so little current required to run leds the system will feed into them even with the ignition off, glowing ofr 15 minutes until the systems automatically shuts everything off.
The car has been awesome as a tow vehicle with a 2 tonne Malibu Response LXi to pull, we couldn't be happier, apart from the led issue.

terry@mobilecar

hi, can any one help me please, I have the same fault as the previous chap, ive never had a trailer on my car but when I put either indicator and when ive pressed the brake pedal the trailer lamp fault it illuminated on dash, ive checked the multiplug connector underneath for signs of damp, ive checked the rear lights on car as well as bulbs and nearby earths, can anyone tell me how to sort it I would be most grateful

flybd5

LED trailer lights will not work with a regular trailer wiring adapter, you need one for LED lights. However, MB doesn't carry the damn things anymore, and if you go to a u-haul, for example, they don't even know they carry it! https://www.etrailer.com/Wiring/Tow-Ready/TR20141.html

N_Jay

On my GL (Factory tow package) works with LED lights but likes to show trailer light out warnings.

Works fine with regular trailer lights.

Never shows a trailer error when nothing hooked up.

flybd5

if u don't use the correct adapter you will blow a fuse, bulb or circuit.

N_Jay

Have had zero problems with fuse blowing.

Not sure why drawing less current (and tripping the bulb failure warning) could cause any issues.

Also, from what I have been told, seems in general the trailer lighting configuration (as standard) follows the brake light type. GLs with regular tail lights expect bulbs in the trailer, and GLs with LED tail lights expect LED trailers.

flybd5

...yet. MB engineers are not good enough to deal with this simple issue. I know, I live in Germany and have to deal with their crappy designs daily.

N_Jay

Overdesigns usually.

I still don't believe that running LEDs is going to cause blown fuses, and if it causes other issues, I would be very surprised.

theswede

Well that can’t be totally right.. 🤔
I have LED tail light and w LED trailer it won’t work without LED converted adapter