Towing Caravans with LED Road Lights

The one thing I have noticed when you plug the van in to the car socket is the reassuring green light on the ATC thingy.

If the tow car provides trickle charge to the leisure battery, after taking care of the vehicles electrical requirements, then a relay in the caravan’s road lights circuit could be fitted so as to operate the LED lights via the leisure battery.

Concerning caravan trafficators, some years ago some vehicle manufacturers made the “bulb failure warning light” the sole means of confirming that all road lights were working and this includes the caravan as that circuitry is identified by the tow car’s system.    This deviation from the norm was accepted in principle by the UK Department for Transport.   I questioned the position in 2005, when I got my first car with this arrangement. I still have somewhere the confirmatory letter from the DfT. 

I’ve got a new Swift caravan with led road lights my towbar fitter asked if the van had led lights and fitted a different relay.  Now towed over 400 miles without any road lights problems.

I had a 2016 swift Elegance with LED lights and a 2016 Discovery Sport. Although the road lights all worked the following issues arose. The 'trailer' indicator on the dash display did not work.  Worse still when reversing the car reversing sensors sounded as it thought it was too close to an obstruction. The problem arises because the wattage rating of the LEDs is too low to register that a trailer has been connected. You need a Sargant VLM 4 box (go to their web site) It costs about £40 and you should have your caravan chassis number handy as you get a discounted price of about £10. It is possible to fit the device yourself.  Under the left seat at the front inside of the caravan the road lights wiring can be found and there are two snap link plugs which you part and plug the unit in between. It is impossible to get it wrong as the plugs are colour coded and different fittings. It was fiddly as there was not a lot of room in my caravan and I had to fit the device between the bulkhead and the seat strut. It worked perfectly though.