Wendy
This type of problem is fairly common. As laurie suggests it is probably the earth.
See the following from Tony Maris which has served me well for years.
Cheers
Dustydog
There is a cure for this. See the following taken from Tony Maris's website www.towitall.co.uk
12s Pin Burn Out. Is There a Cure?
What Is The Problem?
Up to October 1997 and the introduction of new wiring standards for caravans and leisure vehicles, all the 12S system (with the exception of pin 1, yellow, reverse) relied on one heavy wire (pin 3, white) for the earth return. Pins 5 (brown) and 7 (black) were unused. Since EN1648-1, the central pin 7 (black) has been allocated as the refrigerator earth return and pin 2 (blue) is now redundant (previously battery charging circuit). These changes roughly coincide with the introduction of new larger fridge/freezers which, naturally, draw more current.
Pin 7 is an extended male segmented pin in the plug and acts as the ?lead? to guide the plug into the socket. As such, it is the one pin most likely to suffer damage in use. This, coupled with the higher current draw and the smaller cross sectional area of the wire is causing voltage drop, higher resistance, heat build up and consequently, melting plugs and/or sockets.
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
The writer has been Proprietor of Towbars & Trailers (Chesterfield) for over 20 years and lectures on Towbar Installations and Trailer Maintenance to members of the industry. He is a Council Member of the NTTA, is a founder member of the ?Quality Secured? working group and is currently chair of the NTTA?s I.T. working group. His company was the first in the UK to be accredited to the NTTA?s ?Quality Secured? standard. Additionally, he was the founding Treasurer of the re-formed Chesterfield and District Small Business Club and is a D.O.T. and RYA certified Yachtmaster (Offshore).
Supplementary to the above, tests performed by students on the last 3 NTTA courses have produced an improvement in the voltage drop to the fridge of 1.1 volts when using the two links as described. Towbars & Trailers as a company have been earthing the brown wire (pin 5) on all our towbar fittings since late 2001 and implementing the alteration to our customers caravans at their request. There has not been a single repeat instance of pin burn at this time (5/1/2003).
Disclaimer
The information in this guide is as accurate as the writer is able to make it, however, no responsibility can be accepted for any inaccuracies which may be in the text. It is the responsibility of any person wishing to depend on the facts to check for themselves with original documentation or any updating regulations, instruments or changes in the law. Interpretation of the law is a matter for the courts.
Copyright 2001 Tony Maris.
Tony Maris.The writer has been Proprietor of Towbars & Trailers (Chesterfield) for over 20 years and lectures on Towbar Installations and Trailer Maintenance to members of the industry. His company was the first in the UK to be accredited to the NTTA?s ?Quality Secured? standard.
Towbars & Trailers Davian Works, Storforth Lane Chesterfield S40 2TU Tel: 01246 202543 Fax: 01246 551119
? Towbars & Trailers 2002 Designed & Maintained by WebXeL.com
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