Relay Switching 40A This relay is suitable for most 12V functions in cars, boats, trucks, and is used to connect headlights, fuel pumps, horns, fan motors, or other power consumers. Note : This relay is not intended for use with LED auxiliary lights/signals that use pulse power, such as those with flashing functions at short/quick intervals. These can cause short circuits and overheating of the relay. Wiring : Pin 30 : Connect to the battery. Pin 85 and 86 : Connect one of them to ground and the other to control plus. The pins are polarity-independent as they control the relay coil. Pin 87 : Connect to power consumer. Pin 87a : Connect to power consumer. Pin 30 Should be connected to the positive battery terminal if the relay is to supply a positive voltage. Or Should be connected to the negative battery terminal if the relay is to supply a negative voltage.