Electric Relay Kit - For Frostbite Fan/Shroud Sys

The Holley Electric Relay Kit for Frostbite Fan/Shroud System (model FB403) is a precision cooling control module designed to automate engine fan operation in vehicles equipped with Frostbite electric fan assemblies. This relay kit functions as the intelligent hub between your coolant temperature sensor and the electric fan motor, engaging cooling precisely when thermal conditions demand it and disengaging when temperatures stabilize—eliminating unnecessary parasitic load on the engine and improving fuel efficiency.

The kit features a factory-calibrated thermostat set to engage the fan at 185°F and disengage at 170°F, a thermal hysteresis design that prevents rapid cycling and relay chatter. The system includes a 1/2-inch NPT thread temperature sensor—compatible with standard engine block bosses—along with the complete relay harness assembly. This configuration works universally across domestic and import platforms, making it suitable for street rods, classic cars, custom builds, and modern vehicles where OEM cooling management is unavailable or unreliable. The relay's solid-state design eliminates mechanical contact wear, delivering decades of consistent performance without maintenance.

Builders and enthusiasts choose this kit when upgrading to high-output electric fans, installing custom radiators, or rebuilding cooling systems on vehicles without modern engine computer control. The 185°F setpoint is calibrated to prevent boiling in street-driven vehicles while the 170°F cutoff margin reduces cycling frequency during highway cruising. Direct sensor input eliminates dependence on gauge readings or aftermarket controllers, providing automatic, repeatable temperature management across varying ambient conditions and driving loads.