If the rear light clusters have not been handle by the human hand since the C/van was built time to remove them and clean them up then re-try. note where each wire goes so remove one at a time.
If fault the same check again ensure all clean and connected. Then you'll have to look at the tow socket for road lights either clean or change[wiring below]
Whatever you do before disconnection of any wires either take a digi picuture of the socket/plug before dismantling and ensure you see the terminal number and each terminal the wires go in to check the colour and numbers against chart below. No camera take out one wire at a time note the colour and terminal it came out of carry on with rest the same. You then have reference to fit the new plug/socket.
Good luck as electric faults can be a pain in the arse, been there done that.
12N Wiring Code Road lights Black socket.
Pin
Number Colour Function
1 Yellow Left indicator
2 Blue Fog lights
3 White Earth
4 Green Right indicator
5 Brown Side light
6 Red Brake lights
7 Black Side light
The indicator circuits must have a warning light or sounder so that the driver knows when the indicators on the trailer are working.
12S Wiring Code, pre 1999 to British standard
Pin
Number Colour Function
1 Yellow Reversing light
2 Blue Battery Charging Via relay in car
3 White Common Return
4 Green Power feed for internal 12v equipment (not fridge)
5 Brown Spare
6 Red Refrigerator (via relay in car)
7 Black Spare
Not sure? or if you lose the info you can look this up on the website.
Bob
May 2011
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