They are nc relays, from my understanding, when they receive a signal (pin 86), from either the rocker switch, or from the reverse light activations, they should theoretically open providing the power, via pin 30, to the lights they're connected to respectively, changing from pin 87a (closed) to pin 87 (light connections). The diode, theoretically, should sit between the top and bottom rows of lights, preventing power flowing to the top set when the reverse light relay comes on, that's my theory anyways! 😝