12S Melting Pin

[woodsieboy]

I know this used to be a common problem and it seemed I had cured it on our Shogun/Wyoming by always widening the centre pin on the caravan grey plug before connecting, but noticed that both the centre pins on car and caravan had started to melt the plastic again. I have replaced the plug on the cravan no problem. I have replaced the one on the car and in doing so noticed the centre black earth lead was poor cotact due to corrosion and not enough insulation removed from the wire.This was original fit when tow bar was fitted by fitter.My questions are;

As the white earth lead is thicker than the black would I be better to swap the white for the black to get better earth, or could I join the white and black earth leads together to improve the earth, if so is it better to bridge between them, or replace with one heavier duty wire connected to both terminals and taken back to an earth point seperate from the grey cable.

 

[Dustydog]

Keith

I have used the solution below on two caravans. Never had a melt down since.

Hardest part was finding a decent earth on the car.I had to remove some of the boot trim.

Thanks to Tony Maris

Cheers

Dustydog

And The Answer?

You could change your double socket system on car and caravan to one of three continental 13 pin plug systems (either Jaeger or Feder/West Multicon). This, however, would entail changing other caravans and trailers that you may want to tow (though the Feder/West Multicon sockets will accept a standard 12N plug in the centre),and would prove expensive.

Alternatively, you could do a minor modification to the caravan 12S plug wiring. As pin 5 is unused, it is possible to link pin 7 to pin 5 and (provided the brown wire is earthed in the towing vehicle) share the load between both. Additionally, as pin 2 is now unused (though still probably connected to the split charge relay) the same can be done with the feed by linking pin 6 to pin 2.

The advantages are obvious. The combination of 2 cores gives a greater CSA than called for in the legislation and the load (feed and return) is shared by 4 pins instead of two. There will be less voltage drop, less resistance and less heat build up. It is a relatively simple DIY alteration and is inexpensive.

I would recommend using 28/0.30 (17.5 amp) cable for the linking wires.

Tony Maris

Towbars & Trailers, Chesterfield 28/08/2001

 

[WatsonJohnG]

Keith

I have used the solution below on two caravans. Never had a melt down since.

Hardest part was finding a decent earth on the car.I had to remove some of the boot trim.

Thanks to Tony Maris

Cheers

Dustydog

And The Answer?

You could change your double socket system on car and caravan to one of three continental 13 pin plug systems (either Jaeger or Feder/West Multicon). This, however, would entail changing other caravans and trailers that you may want to tow (though the Feder/West Multicon sockets will accept a standard 12N plug in the centre),and would prove expensive.

Alternatively, you could do a minor modification to the caravan 12S plug wiring. As pin 5 is unused, it is possible to link pin 7 to pin 5 and (provided the brown wire is earthed in the towing vehicle) share the load between both. Additionally, as pin 2 is now unused (though still probably connected to the split charge relay) the same can be done with the feed by linking pin 6 to pin 2.

The advantages are obvious. The combination of 2 cores gives a greater CSA than called for in the legislation and the load (feed and return) is shared by 4 pins instead of two. There will be less voltage drop, less resistance and less heat build up. It is a relatively simple DIY alteration and is inexpensive.

I would recommend using 28/0.30 (17.5 amp) cable for the linking wires.

Tony Maris

Towbars & Trailers, Chesterfield 28/08/2001

You beat me to that !!

 

[John_miller]

A further vote. The 12S pin on my new Bailey burnt out in the first year, so I did the Tony Maris modification. 2 years on - no further problems. The car earth was the hardest part, simply because the towbar fitter had cut the unused wire, so I had to join on a new bit before attaching it to a previously used earthing point. Took me around about an hour all in.

John M

 

[WatsonJohnG]

I used 2.5 mm single strand insulated mains cable to make small U shaped jumper wires

They've been fitted to my curly cable for well over 10 years with no more melted centre pin

 

[gary]

I used a small adaptation of Tony Maris's method, I used the spare brown wire but fully connected it from car earth to fridge earth at the fuse box in the van.

No more melting but also a higher voltage to the fridge making it more efficient while towing

 

[SteveW77]

Just change the car & the van to the 13 pin system and solve the problem once and for all.

Steve W

 

[Dustydog]

Hi Steve

13 pins may solve the problem but at quite a cost of rewiring the car and caravan plus parts of course.

Cheers

Dustydog

 

[SteveW77]

I did mine myself for less than

 

[Dustydog]

Steve

That's not bad at all. How easy / difficult was it?

Did you use the splitter things on the caravan or renew the whole harness? I'm interested but can confirm the Tony Maris mod has worked perfectly for me on my last two caravans.

Cheers

Dustydog

 

[woodsieboy]

Hi Everybody and thank you for all your replies, now I must be particularly thick at the moment because the brown 5 wire in the caravan plug is labelled sensing device, the 2 earths are white3 and black7.

Please John Watson can you confirm your cure, did you bridge black and white together in car socket, and also the caravan plug? Or if not which wires did you bridge.

Thank you in anticipation

 

[SteveW77]

I purchased the cable & fittings from Sargeants electrical supplies ( Just google Sargeants ). Get a wiring diagram off of the web and just take your time. I wired all the way back in to the van, but you could always join the existing wiring using suitable connection blocks. The problem is with the poor quality connectors, not with the wiring itself. The 13 pin connection is better in every way. I find it helpful to take digital fotos of all connections before I disturb them, then you have always got them to check if you go wrong at any stage

Steve W

 

[TD42]

Hi Keith have a look at this website http://www.towitall.co.uk/faq/faq1.htm

 

[Dustydog]

Thanks Steve

I think I can manage that especially as I have already been deep in the car boot!

At the moment the Tony Maris fix is working well but maybe in the future I shall go in your direction. It's good to know there are now two alternatives.

Cheers

Dustydog