Fan Relay W/ Thermostat

The Fan Relay with Thermostat (PWI30103) is a complete thermal management kit designed to automatically regulate engine cooling fan operation based on coolant temperature. This relay system activates the cooling fan at 185 degrees Fahrenheit and disengages at 175 degrees Fahrenheit, maintaining optimal engine temperature in vehicles where fan control is critical to performance and longevity. The kit includes a precision 3/8 NPT temperature sensor, 1/2 NPT adapter, and integrated harness assembly for straightforward installation.

The thermostat relay operates on a dual-point control strategy: activation at 185°F prevents engine overheating during sustained operation or high-load conditions, while the 175°F cutoff minimizes parasitic drag from fan operation during normal cruising, improving fuel economy and reducing unnecessary mechanical stress. The 3/8 NPT sensor threads directly into engine block coolant passages for accurate real-time temperature monitoring. The included 1/2 NPT adapter accommodates variations in coolant port configurations. Complete harness and relay assembly handles power distribution to the fan motor, eliminating the need for custom wiring or external control modules.

This thermal control kit is essential for engine builders, hot rod enthusiasts, and motorsport applications where factory cooling systems require supplemental or independent fan management. Common use cases include high-performance vehicles with upgraded radiators, engine swaps where original fan circuits are incompatible, and track-focused builds where precise temperature control prevents detonation and maximizes power output. The kit is also suitable for off-road and marine applications where consistent cooling performance under variable load conditions is non-negotiable.

For buyers evaluating cooling solutions, a thermostat relay offers greater precision than mechanical fan clutches or fixed-speed setups. The two-point switching band (175–185°F) reduces thermal cycling, extends engine component life, and delivers measurable fuel economy gains by preventing unnecessary fan engagement. Compact dimensions and field-proven design make this a reliable component for both restoration and new-build applications where cooling consistency demands verification and control.