Troubleshoot your Tail and Brake Lights

David Cook — 20 December 2018

Before every journey – whether it be one kilometre or a thousand – you should check your trailer’s brake and tail-lights. An assistant need only stand behind while you go through a sequence of blinkers, the brakes and the tail-lights.

Should you find a problem with a light with any system, the first place to check is the seven/12-pin plug adjacent to the hitch, which connects your camper’s electrical circuits to those of the tow vehicle. The pins in the plug can lose a good contact with the plug socket on the car. This can be a result of dirt – ensure they are clean – but it’s more likely to be from the two halves of the split pins on the plug connected to the trailer being crushed together. Use a pen knife or narrow blade to separate the two sides of each pin until they are parallel and not in contact with each other, and reinsert the plug into the female plug on the car.

If you still do not have lights, check the tow vehicle itself. If you do not have tail/brake lights on the tow vehicle check the circuit fuses in the vehicle, as these may have blown. Unplug your trailer and replace the fuse(s) as necessary. If they blow immediately upon the lights being used, then you have an electrical fault somewhere in your vehicle and may require an auto-electrician to trace and find it. If okay, reattach the trailer’s seven/12-pin plug and try again. If the circuit fuses again, then you have an earth leakage somewhere in your camper’s circuits. This could be from a fault in the seven/12-pin plug itself (such as a strand of wire from one wire/pin touching an adjacent wire), or a broken wire or some point where the insulation has broken down or been removed from the internal copper conductor and it has come into contact with other wire(s), the bodywork or chassis of the van. This can only be remedied by a careful inspection of every centimetre of the wiring.

Also closely inspect the point of attachment of each wire with the lights themselves. LED lights, as used on most modern vans and trailers, are usually supplied as a unit and are generally fault-free and waterproof. However, older globe-based light assemblies are often subject to problems with faulty contacts between the globes and their terminals within the light fittings, or with failure of the globes themselves.

Remove and inspect each globe as necessary. Replace any faulty globes. Use fine sandpaper to clean the contact points on the globes which appear to be okay and the contact tabs on the light assemblies. Reinsert the globes, ensuring a good contact and test again. This may require bending the tabs inwards slightly to ensure a good contact with the ends of the globes.

Boat trailer lights, which get regular dunking at boat ramps, can suffer from bad corrosion of light globe metal components and internal tabs in the assemblies. Clean as necessary and use a water dispersant spray to assist in future protection. Take care with reassembly of the light fittings to ensure gaskets do their job of excluding water from entering the light fittings in the future.


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