Finally got round to fitting the second (12S) socket today using the NP107 relay supplied. All looked fine but when I connect the socket to the caravan, the relay constantly switches on and off at about 2 second intervals? Is this right? I assumed that once the car voltage had reached a set level, the relay would switch on and stay on until the voltage dropped? Looking at the fridge while it's connected I see the 12V light switching on and off all the time. Have I got a duff relay unit?