im guessing that 2 pins are earth and two positive? one would be positive for the light and 1 earth for the light and the other 2 positive and earth for staring the car? i assume if you solder all 4 pins to just the two ignition wires thats what causes the light to go out once the car is running??

do you really need a relay for this as it just connects onto the exsisting wires and does the same job just without turning the key for a 3rd time?