Towing 13 pin electrics, problems on factory fitted tow bar

[DCL]

My Transit Custom with a factory fitted tow bar recently stopped detecting the trailer. All the lights stopped working correctly but the brakes lit up all the lights, except the flashers.

After having the trailer checked out the fault looked like the transit so took it was taken to the dealer who reported 'no fault found'. But they did reset something as all the dash data was zero'd. It then all seemed to worked again.

Is there some form of fail safe on the tow electrics? I can't understand how the 13 pin wiring can result in such behavior without it being a deliberate mode. How does it detect the trailer? Seems to work with, or without, pin 12 grounded (the 13 pin plug spec for that purpose).

[BHM]

My 14 plate factory tow bar had a crap socket (verdigris and connectors looked to be further recessed than others that I have).

Anyway after loads of annoying grief I unplugged it at its connector, chopped it off and wired an aftermarket one in.

Jobs a good-in

Bloody Ford (even though its some German socket)

Bloody Germans

BHM