I have an issue with the electrics on my Range Rover P38 whenever it’s hitched up to a trailer.
All the lights operate as they should when checked, except when indicating and braking at the same time. If I indicate left and push the brake pedal, the trailer indicates right; if I indicate right and brake, it indicates left. This is obviously potentially dangerous so I’d appreciate your advice.
Nat Dawkins, Somerset
Your trailer earth is faulty - probably disconnected. It’s the white wire going to pin No 3 that makes the earth connection to the vehicle.
Dismantle the trailer plug and check the white wire to pin 3 is connected and rust-free. If you find no problem, check the back of the vehicle’s socket. Sometimes a wire is run from one light to the other to provide the earth for both lights and this can be corroded or broken.
This workshop advice appeared in the May 2015 issue of LRO. Back issues are available to download on digital devices here.