Tow bar electrics

[glenw216]

Hi
I'm after some information on tow bar preparation ,my 2016 sprinter has it apparently but where is it ?
What do I need to plug into it ?
I did acquire a Mercedes towing socket, this had two box connectors on the end but I think it's from a later model ,I'd rather go this way if possible rather than the bypass relay and more wiring
Any help would be most appreciated
TIA

 

[oscarham]

Hello Glen,

I am a trailer & towbar fitter. If you order a good quality electrics kit (I always use Conwys), it will come with complete instructions so you will know where the connections are.
Failing that, if your kit has any part numbers or brands on it, it may be worth googling it to find the brand then try to find their fitting instructions.
By all means reply to the thread or send me a message and i can help you further.

Oscar

 

[Jim2]

Hi Oscar, nice to know that there's an experience towbar fitter on the Forum!!! So far. I'm on my 3rd MB E class, the latest being a 2018 MB 220 E class w213. Previous to this, I had a 2010 E class, w212, and fitting the towbar was a doddle, same with the wiring, just piggyback onto a bypass relay, wire for wire, and off you go. Next one was a 2014 E class w212, and fitting the tow bar was like its predecessor, it too was a doodle. No doddle when it came to the wiring though! Actually, to be fair, it was a doodle to until it came to the brake lights, The park and brake light use the same cable, and bulb/LED (its not a bulb in the accepted sense, I don't know the correct term.) But when the brake pedal is pressed, more power is sent to the brake / park light, causing the LED to glow brighter. (Does that make sense? ) Anyway, I could not get the brake light to work while the park lights were on. I even used a more expensive bypass/relay / that was supposed to differentiate between what power was being sent to the LED bulb. The only solution was to take separate brake light feed from the brake light high in the rear window, and that worked fine. Now, I have graduated to MB Nr 3, it's an 2018 MB 220d, w213, and of course, the towbar question arises again. First out of the box, are the w212 and w213 towbars interchangeable? Second, can I use the relay bypass system as I've done in the two previous MBs? Some info about myself Oscor, though now retired I've spent many years in the motor trade, and seen some great changes and advances, and of course modern electronics and computerisation leave me scrabbing around, in a world I'm far from comfortable in. But anyway, that's life!!! Any help you can give will be most helpful,
Thanks, and All the Best, Jim.

 

[oscarham]

Hi Oscar, nice to know that there's an experience towbar fitter on the Forum!!! So far. I'm on my 3rd MB E class, the latest being a 2018 MB 220 E class w213. Previous to this, I had a 2010 E class, w212, and fitting the towbar was a doddle, same with the wiring, just piggyback onto a bypass relay, wire for wire, and off you go. Next one was a 2014 E class w212, and fitting the tow bar was like its predecessor, it too was a doodle. No doddle when it came to the wiring though! Actually, to be fair, it was a doodle to until it came to the brake lights, The park and brake light use the same cable, and bulb/LED (its not a bulb in the accepted sense, I don't know the correct term.) But when the brake pedal is pressed, more power is sent to the brake / park light, causing the LED to glow brighter. (Does that make sense? ) Anyway, I could not get the brake light to work while the park lights were on. I even used a more expensive bypass/relay / that was supposed to differentiate between what power was being sent to the LED bulb. The only solution was to take separate brake light feed from the brake light high in the rear window, and that worked fine. Now, I have graduated to MB Nr 3, it's an 2018 MB 220d, w213, and of course, the towbar question arises again. First out of the box, are the w212 and w213 towbars interchangeable? Second, can I use the relay bypass system as I've done in the two previous MBs? Some info about myself Oscor, though now retired I've spent many years in the motor trade, and seen some great changes and advances, and of course modern electronics and computerisation leave me scrabbing around, in a world I'm far from comfortable in. But anyway, that's life!!! Any help you can give will be most helpful,
Thanks, and All the Best, Jim.

Hello Jim, first of all apologies for the delay in my response.
For a start, it's not recommended to remove and refit towbars regardless if they fit or not - strictly speaking you should use all new fixings and by the time you take the first car apart to remove the towbar and put the car back together again you may as well buy a new one.
With regard to your towing electrics woes: the bypass relay you mention is essentially a way of cheating the CANbus system in order to get towing electrics fitted more easily and often in a more cost effective manner. Commonly when fitting a Vehicle Specific Kit (VSK) the vehicle needs coding otherwise the electrics may not work and you can also experience a barrage of error codes and vehicle faults. A towbar fitter will be able to tell you if the car needs coding or not - these days most vehicles do need coding so a bypass relay is a good way around this problem.
As to whether you can fit a bypass relay to your new car: by all means, go for it. As you have previously experienced, be cautious of lighting systems using a pulse width modulation system (PWM), this is the reason you had to use the top brake light for the signal. PWM systems send a lower voltage for sidelights (often 6v) and will send a higher voltage for the brake lights, usually 12v. As you said, a more expensive bypass relay (the Logicon unit from PCT is very good) can usually differentiate between the voltages.
You sound familiar enough with electrics to tackle this task so I'm sure you'll be fine, unless you've done it already.
Cheers, Oscar

 

[Jim2]

Hi Oscar, Thanks for the very informative reply. The Relay I used was the Ryder TF2218/7H Smart Logic, was supposed to differentiate between the park / brake lights. But it didn't, unfortunately. The Logicon unit from PCT will be the one to go for this time round, for sure. Even though I now have the car a little over the 3 mths (and out of guarantee) I haven't gotten around to fitting the towbar yet... a job for the spring, I think. So far, I've only driven something like 1200 Klms, mainly because I was out of the country for 5 weeks, but I expect that will change, now that I'm back home again. While I always use the original bolts re-fitting a towbar, I use new locking nuts, and a generous dab of thread lock. As for re-moving the tow-bar, in Ireland (probably in the UK, too!) There's logic behind it as well! A car with a towbar fitted, gives out the wrong signals to prospective buyers, and as a result, lessens its trade in value at the dealership. So off it comes, even if I'm not replacing it with the same model. I have currently "in stock", a 2003 Audi A 6 (one of the best cars I ever had) a 2016 Skoda Octavia, a MB W212, and a 2016 Peugeot 2008. towbars! Anyhow, we will see how it goes...
Thanks again for your advice!!
Jim.