S212 2015 E350 Towing Electrics

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scgfull

Active Member
Joined
Nov 19, 2006
Messages
272
Location
Hampshire
Car
E350 Bluetec Night Edition Estate & CLK 350 Cabriolet AMG Sport
I have ordered a new E350 Estate with a factory fit towbar with 13 pin socket.

I am hearing, through various sources, that the wiring to Pins 9/13 are only rated and fused at 15 Amps. A lot of new trailers and virtually all new caravans now come with a trailer ABS type system (ATC for ALKO chassis and IDC for BPW chassis). These systems can draw up to 20 Amps through Pin 9/13.

Clearly a circuit gauged and fused for 15 Amps would fail.

I have asked on a number of occasions for the dealer to answer this but have not had any response.

Can anyone check to see what fuses they have on a similar car setup.

Thanks

Steve
 
This, taken from the E class price list

"Tow bar, manually folding – includes 13-pin socket
When ordering this option, please discuss with your Retailer any specific
electrical towing requirements"
 
I recently had a towbar retrofitted and it came with a supposedly OE Westfalia wiring loom. Irrespective of what fuse is fitted (and it is 15amp) the cables in this loom are not of the cross-sectional area that would support anything greater than 15a current. This despite me interrogating at length the supplier of said loom. Very disappointing since I tow a caravan and this, I feel, needs more than 15a to successfully supply the fridge and battery when underway. Compared to the 'old' 7 pin socket and cable it's not good although I do prefer the newer setup for its ease of working.
 
This, taken from the E class price list

"Tow bar, manually folding – includes 13-pin socket
When ordering this option, please discuss with your Retailer any specific
electrical towing requirements"


Yep and this was done at the time of ordering and has been reiterated several times since but I have had no acknowledgement that this will actually be complied with. This is why I am asking from those that have the factory fit.
 
I recently had a towbar retrofitted and it came with a supposedly OE Westfalia wiring loom. Irrespective of what fuse is fitted (and it is 15amp) the cables in this loom are not of the cross-sectional area that would support anything greater than 15a current. This despite me interrogating at length the supplier of said loom. Very disappointing since I tow a caravan and this, I feel, needs more than 15a to successfully supply the fridge and battery when underway. Compared to the 'old' 7 pin socket and cable it's not good although I do prefer the newer setup for its ease of working.


Thanks Druk.

This is precisely the sort of issue that I want to rule out early - something for me to actually check when I am conducting the handover from the dealer.

Steve
 
Short of running a heavier cable through the loom and fitting a stand-alone relay at the rear sam, which is the option I'm pursuing, you could supply the ATC from the caravan battery and allow that to be charged from the 15amp fuse. Be aware that one of the two power leads, 9 or 13, not sure which, is a direct feed from the sam and not relayed. So, when the ign is switched off, there is still power to this cable and if this is connected to a consumer will drain the car's battery. Given the number of German caravanners there are you might well wonder why they hadn't solved this little mystery years ago. It was the same set-up on my 2003 factory fitted S211.

PAH! :dk:

And don't expect any assistance from a main dealer. They won't have a clue what you're on about.

End of story I'm afraid. Been there.....done that.







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Are you sure the rating isn't 15 Amps per pin? If it were, then both pins ought to support a 30 Amp load, but I guess that depends on where the power is coming from. I would have also thought that a caravan's own battery ought to be able to supply shorter term high loads. Probably best to consult a towbar/caravan expert if you can.
 
Are you sure the rating isn't 15 Amps per pin? If it were, then both pins ought to support a 30 Amp load, but I guess that depends on where the power is coming from. I would have also thought that a caravan's own battery ought to be able to supply shorter term high loads. Probably best to consult a towbar/caravan expert if you can.


Hi Gordon,

The circuit is: - Pin 9 supply with Pin 13 return(earth) so that they are in series not parallel. Each leg of the circuit needs to be able to take the maximum load.

Steve
 
Additionally it is Pins 10/11 that are also paired - Supply 10; Earth 11.
 
Hi Gordon,

The circuit is: - Pin 9 supply with Pin 13 return(earth) so that they are in series not parallel. Each leg of the circuit needs to be able to take the maximum load.

Steve

Additionally it is Pins 10/11 that are also paired - Supply 10; Earth 11.

In which case my reply above re: unswitched feed should read pin9 or pin10. I'm not at home at present and can't check. 9+10 should give 30amps possibly but would need an ign triggered relay to be of any use. And then the caravan wiring would need modified to accept the current from two sources. Which then precludes you from using a non-modified van. Better if the thing was done to pattern from the start.




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Thanks Druk,
So can you tell me what fuse numbers are associated with the towbar wiring please.

Thanks
Steve
 
A thousand miles from home when you posted. Give me some time Sunday and I'll dig out the diagram.
 
And responded. Thanks
 
For the benefit of others who may be towing caravans fitted with ATC anti-snake and with a factory-fit or OE aftermarket wiring kit this is the repeat of the PM sent to scgfull of a conversation I've had with towbar suppliers PF Jones.

"Steve.

I've been in touch with PF Jones who, in turn, got in touch with Westfalia and the bottom line is that your car will have 15amp fuses and cable. As does mine. This is because it's an industry standard across the board to have 15amp . That is...every manufacturer has the same. Where the problem lies is with Alco who have designed the ATC to require 20amps. According to Westfalia that is, and Merc et al are unwilling to conform to a 20amp standard just to suit Alko :dk:
PF Jones suggest running a 20amp supply cable through the loom to pins #9 and #13 and fusing the sam to 20amps.

Derek."




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