W166 towing electrics

[nigelcorby]

Caravan fridge not powered when towing.
Hi, I have a 2014 ml 350 (w166). Not seeing any voltage at pin 10 on the towing electrics, hence I’m not getting any power to the fridge when travelling.
I’ve checked all the fuses in the fuse box under the passenger seat. All those present are ok but 111 and 115 are not present.
can anyone advise which fuse is connected to pin 10 on the towing socket (13 pin type). I can’t be sure if this has ever worked since I bought the car.

 

[Bobby Dazzler]

Caravan fridge not powered when towing.
Hi, I have a 2014 ml 350 (w166). Not seeing any voltage at pin 10 on the towing electrics, hence I’m not getting any power to the fridge when travelling.
I’ve checked all the fuses in the fuse box under the passenger seat. All those present are ok but 111 and 115 are not present.
can anyone advise which fuse is connected to pin 10 on the towing socket (13 pin type). I can’t be sure if this has ever worked since I bought the car.

Is it a factory fitted towbar? I'm sure I read somewhere that factory fitted towbars don't come with the fridge circuit active, and needs to be sorted here. You might want to check. My w164 is the same.

 

[nigelcorby]

It’s not factory fitted but was fitted by a Mercedes dealer and supplied by Mercedes I believe.
I‘ve been searching for a wiring diagram but no luck so far.

 

[Bobby Dazzler]

It’s not factory fitted but was fitted by a Mercedes dealer and supplied by Mercedes I believe.
I‘ve been searching for a wiring diagram but no luck so far.

I also have a car with the same Mercedes supplied and fitted, and that also doesn’t have the fridge circuit active. I didn’t mention it though as it’s a very rare thing to do, it costs a fortune - the previous owner of your car had deep pockets or money no object approach to their car

 

[BTB 500]

If you check the 13 pin socket you will almost certainly find there are no wires to either the switched or permanent live connectors. I got a mobile specialist to come and wire them up on my Vito (which has a factory towbar & electrics) - he said this was quite common on Mercedes. IIRC the W167 does have the connections, but the 166 doesn't. Apart from running a fridge (and charging the battery) on the switched supply, the permanent live is needed for AL-KO ATC (stability system) which is standard on many caravans nowadays.

 

[nigelcorby]

I have the permanent live because the Al-Ko works when I plug It in. I’ll strip the socket off when the weather dries up and see if pin 10 is connected. If necessary I’ll have to fit an after market bypass relay. I do long trips so can’t be without the fridge powered up. Bit of a drop off on Mercedes part if they’ve left it out!