Towbar Electrics


A thorny issue! All vehicles that tow or carry anything at the back that blocks the vehicle rear lights, Numberplate or reflectors (from directly behind or an angle) need to have fitted, a set of lights and reflectors (like a lightboard). These need to work! To power this the car has a socket that the trailer lights plug in to. This socket duplicates the lighting signal of the car rear lights and allows an external lighting source to be powered from it.

Simply explained how it works

Traditionally all the wiring joins the cars electric loom at the rear. This is still pretty much the case except that because vehicle electrics have become very much more complicated newer vehicle electrics have to be protected from overloading. This is done in several ways.

The traditional way is to connect the trailer wiring direct to the vehicle lighting loom. The protection comes from the vehicles own fuse arrangment. If a short circuit occurs then the fuse in the fuse box blows.

bulb failure

Now some vehicles have systems that monitor the vehicle lights and if a light fails the driver is informed usually by a signal to the dashboard. [This is because the electrical balance has been upset]. In this case when another bulb such as a trailer light is attached than the car signals the driver that a lighting fault has occured.

To stop this happening we fit a bulb failure bypass system. This completely protects the car from power fluctuations and short circuits in the trailer. This works by monitoring the car lights and then duplicating them to the trailer lights using its own power supply. The car simply doesn't know it is powering trailer lights.

This now has a draw back on most new generation of cars. The bulbs are sometimes powered by a fluctuating current, so that one bulb brightens as needed and performs two tasks. This is covered by a different module.

We now have multiplexed CANBUS electrical systems in vehicles. This is a computor controlled system that usually uses a "plug in" trailer electrics. This system integrates the towing electrics to the cars on board computor. The car then knows that a trailer or lightingboard is behind and will sometimes alter some of the braking and suspension characteristics.

Here at Ambrow Trailers we will fit the system suitable for your vehicle with a full choice of solutions for your trailer and caravan lights.

Heres an example of a typical dedicated wiring kit being fitted to a VW T5 transporter.