Feliks Soe

Car 2008, 320d, 4matic.
there is no power to the trailer. I have to state that electricity comes to one contact. This is the charging current. nothing for the trailer lights. I read the forum and found information where there may be water damage. I checked . yes SAM had gotten moisture. I detected it by opening SAM. there was about two square centimeters of white corrosion in the lower left corner. I removed it with microcircuit cleaner. plate clean and dry, I put it back together and mounted it back on the car. this well-known error where the water comes from under SAM, I also found it and removed it. as the rear light assembly seal ages, it deforms and lets water in. I installed a new gasket. things back in place and still no electricity. I live in a place where the Mercedes Star program is not available. a mechanic local scanned the SAM and we were able to enable and disable the trailer. we tried to test the relays but without results.

Tsumi

I think the next step would be to replace the SAM. The SAM sends power directly to the lights; there is nothing else between the SAM and trailer lights.

lkchris

Just FYI … my trailer wiring works fine, but when I connect a circuit tester to the plug it doesn’t work.

alive19

I had a nightmare getting LED lights to work.

There is a lot going on with the sensors. But you should be able to get some power readings (noting that it will likely be sensor voltage, so changing). If you have no power on any, then you have a problem. Either fuses or SAM. Either way a scan tool should pick up the issue.

Feliks Soe

f72 is without power. that means , no power from sam to fuse. sam caput.. still looking good price sam.