Modern cars have very sophisticated lighting bulb failure and lamp control systems that constantly monitor the current consumption in individual wires – if towbar hitch wiring connects straight on to the bulb wires the computers can shut down , put on warning lamps or in some cases burn out.
The ADC-7-AS does not use the car’s lighting circuits to power the trailer lights, only to switch them. The ADC-7-AS relay draws only a tiny amount of power from the bulb wires to trigger the internal relay banks – the main output power to the towbar hitch socket is provided from the 12 volt permanent relay power – this prevents the car from detecting the presence of the towbar electrics and also protects the cars circuits as any short or problem with the trailer electrics will blow the fuse for the relay – not the cars electronics.
Some modern cars has one common wire for “stop”and “tail light” or “fog”and “tail light”. ADC-7-AS is capable to recognize and separate that signals automatically. If car has a common wire for “stop”and “tail light”, the “bn” and “bk” wires should not be connected. Only “rd” connected to this common wire. If car has a common wire for “fog”and “tail light”, the “bn” and “bk” wires should not be connected.Only “bu” connected to this common wire.
Wiring diagram: