The 7 pin N type plug and socket is still the most common connector for towing. This supplies power to the road lighting of your trailer or caravan. This has now been replaced by 13 pin Euro plugs on all new caravans.
Below is a diagram for the original plug and socket showing the functions of each pin.
7 pin ‘S’ type plugs and sockets are usually used on caravans to supply power to the reverse light and give auxiliary power to other systems such as fridges, internal lights and charging systems. This was replaced in 2008 by the 13 pin Euro plug on all new caravans.
It is recommended that a split-charge relay should be wired into your ‘S’ type caravan wiring. At a set voltage this relay will divert the power that usually charges you vehicles battery to the auxiliary systems in your caravan. This is useful for charging auxiliary batteries and powering appliances like fridges and freezers while you are driving. Click here for more information on split-charge relays.
Below is the wiring diagram for this plug and socket.
SUITABLE FOR USE WITH ALMOST ANY 12 VOLT VEHICLE INC AUDI, BMW ,VW, MERCEDES, FORD, SKODA ,VAUXHALL ,LEXUS,VOLVO, JAGUAR (except XJ & S Type and any earthed switched vehicles)
Can be used with either plain or modulated 12 volt circuits
This relay is an essential piece of kit on modern multiplex and cambus equipped cars to prevent damage to lamp control units & ecu’s
How Does It Work???
Modern cars have very sophisticated bulb failure and lamp control systems that constantly monitor the current consumption in individual wires – if you connect towbar wiring straight on to the loom the computers can shut down, put on warning lamps or in some cases burn out !!
The TEB7AS relay draws only a tiny amount of power from the loom to trigger the internal relay banks – the main output power to the towbar socket is provided from the 12 volt permanent relay power – this prevents the car from detecting the presence of the towbar electrics and also protects the cars circuits as any short or problem with the trailer electrics will blow the fuse for the relay – not an expensive ecu!
13 pin full function socket with bypass
This images below show how to wire a 13 pin socket for full function when used for a caravan, using a TEB7AS 7 way bypass relay and TEC3M switch relay.