The Davies Craig mechanical fan switch (#0401) can be used with electric fans or electric water pumps. It senses the coolant temperature after it passes through the engine block prior to entering the radiator and is adjustable from 40° to 100°C (104° to 212°F). The thermal switch is mounted near the radiator and the stainless steel probe is fitted inside the radiator hose. The thermal switch & relay kit enables a fan to operate both thermally and also when the air conditioning is running.