As of January 2012 the wiring of your towbar will now become a testable item on the yearly MOT test.
For some the towbar is never or rarely used or in some cases you have a fault that you were not aware of.
Auto Installs now offer a towbar electric fault finding and repair service that use the same test equipment that VOSA use in their MOT testing,
This insures that your towbar socket is not only working 100% and passes the yearly MOT test but also keeping anything you maybe towing safe and sound.
Caravan and trailer wiring can also be tested and repaired.