W211 Tow bar electrics

nigelstgeorge

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I have the factory fitted detachable towbar with the electrical socket already under the rear bumper but never been used. I plugged in my trailer and the sidelights work but not indicators etc. Do I need to get either a special towing module or a short adaptor cable. Sorry for the question but this is my 3rd Mercedes starting with an E300 CD in 1999, then a W210 E320 CDi upto 114,000 miles and just got a 2005 E320 CDi. The previous two I had aftermarket towbars fitted and they were fine but having now retired and knowing how electrically sensitive the W211 merc is I want to make sure I don't do something stupid which ends costing me more than I would save. Thanks.
Advice gratefully received.
 

television

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The first thing Nigel is to see what make the trailer adapter is

as there are several after mark versions
 
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nigelstgeorge

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E300 Avantgarde 1998,C250 CDi 2000, E320 2002, E320 CDW211 2005. FL2,RRS 2011,GLE 2016
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Malcolm everything on the car is mercedes dealer fitted. The detachable towbar is witter and underneath the car there is what looks like a standard caravan/trailer socket. Certainly my trailer plug fits in perfectly but there does not seem an obvious way to tell how it is wired from the car side. One MIGHT assume that if a UK supplied W211 estate with towbar and electrics is supplied by a merc dealer then it would work with a standard UK trailer!!!!!
 

television

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The tow bar electrics are plugged into the rear SAM you could follow the cable through and see what it says where it plugs in... I do not think that MB use Witter
 
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nigelstgeorge

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OK I will look in the morning. Is the SAM easy to find/identify. Is it some sort of black box. And will it say where the wires go to. Sorry lots of questions. regards Nigel
 

television

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It is all part of the rear fuse box
 
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nigelstgeorge

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E300 Avantgarde 1998,C250 CDi 2000, E320 2002, E320 CDW211 2005. FL2,RRS 2011,GLE 2016
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Hi Malcolm - had a good look but with the DVD SAT Nav right up against the fuse panel it is difficult to ascertain which wires are going to the tow bar socket. Will take it in to a trailer fitting specialist to see if they can work out what is happening. Thanks for your input
 
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nigelstgeorge

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E300 Avantgarde 1998,C250 CDi 2000, E320 2002, E320 CDW211 2005. FL2,RRS 2011,GLE 2016
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Malcolm - update. The relay box was behind the panel above the battery on the offside side. We needed to replace the relay box and the rear socket and now all works.
 

television

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2002 SL500, 216 CL500, all fully loaded
Malcolm - update. The relay box was behind the panel above the battery on the offside side. We needed to replace the relay box and the rear socket and now all works.

Thank you for posting back with that info :D:D
 

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