Got a 54 plate Carens CRDI LX Diesel. Bought it with a tow bar fitted, with just the 12N socket for trailer lights. I want to tow a caravan so need to fit a 12S socket so the fridge and caravan battery can be powered up and charged from the car. Have got a TEC3M combination relay, and the wiring details for it look very simple. (in fact they look too good to be true ) Anyone know of any pitfalls, booby traps or other problems that I should be aware of. Thanks all.