There are a three different options available depending on what you are using the towbar for:
This socket is a standard 'single electric' point which is required for most trailers and cycle carriers. The functions it provides are indicators, tail lights, brake lights and fog light.
These sockets, known as 'twin electrics' are usually fitted if you are towing an older caravan. The 12N (black) provides the road light functions and the 12S (grey) provides a reverse light feed, runs the fridge in the caravan and charges the battery whilst you are travelling.
This socket is also mainly used for newer caravans as it combines the two 7 pin 12N & 12S into one socket for convenience. Most modern caravans are now being manufactured with a 13 pin plug.
This socket can also be required for some bike racks and some new trailers. The advantage of this is the ability to have a reverse light on the trailer which is not standard with the traditional 12N 7 pin socket.
Once you have established which socket arrangement you need, you then have the choice between the type of wiring installed. There are two options:
A vehicle specific wiring kit connects into the existing wiring loom on the car. It is the equivalent to the kit a main dealer would install if they fitted the towbar.
These kits are not necessary on every vehicle, however we usually recommend this kit is fitted if the vehicle is still under manufacturer's warranty or if it has any built in towing related features such as Trailer Stability Program which are only activated by using this kit.
Bypass relays are used where the cars own lamp circuits cannot support their shadow circuits on the trailer or caravan. This may be because the circuit may not be rated to take the extra load of the trailer, or because the cars own bulb failure monitoring system might become confused with the extra load from the trailer lamps. In their simplest form, bypass relays operate by taking a signal current from the car’s lamp circuit, which then switches a relay and with it current to the equivalent circuit on the trailer from a supply derived directly from the car’s battery.
This relay is not designed for a particular vehicle and the light feeds need to be manually connected into. Although this is the cheaper option, it will not activate any towing related features as a vehicle specific kit would.
Most older vehicles do not require a vehicle specific kit or bypass relay, in which case the connections are made straight into the rear lights and a standard buzzer is connected across the indicator circuit as an audible alert of the indicator function on the trailer.
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