I have fitted a towbar and standard 12n electrics, and part way through wiring up the 12s circuit.... But.....
The split voltage relay in the kit (Maypole TEC2), requires a 12v feed and a separate ignition feed. OK....12v from battery with 20amp inline fuse close to battery connection and 30 amp wire, but the instructions say the ignition feed needs to be live when ignition switched on but goes dead during the cranking over/starting up of engine, then comes live again. Suggests wipers feed????
What the instructions don't say but others have told me I need to get done, is when all is wired up, there is a small hole in the relay to allow adjustment to the voltage regulator. ????? Any one know what this is about and how you go about making the correct adjustment please?
When I wired my 12s I used a PCT Volton Combi, same sort of relay just different brand, from what I can remember there was one 12v direct to via a fuse and close to the battery, one to earth. On the other end 12v caravan battery charge, 12v fridge and a permenant 12v live for caravan interior lights.The adjusting pot was for setting up the fridge and charging supply only when engine is running and cuts 12v supply when engine is switched off
The last time I had anything to do with those relays I was informed by a large towbar and trailer company owner that the time of relays that needed a feed from an ignition based source was past. At that time ( nearly 15years ago ) the way to go was with a voltage sensing relay which does exactly the same job simply by sensing when the voltage us higher than a free standing battery could provide. Brilliant device very reliable and cheaper to buy.
Iirr the older devices needed an ignition controlled supply and this generally would be taken from the alternator itself.
------------- Bill
For a licence dated 1997 or later you must add together the plated max weight of the caravan and trailer, if the total is 3500 or less you can tow it. You may even tow a caravan with a MAM greater than the cars unladen mass the restriction was removed in 2013