Automatic Thermostat Switch

The DERALE Automatic Thermostat Switch (model 15721) is a precision engine cooling control component designed to manage coolant flow based on temperature thresholds, making it essential for custom cooling systems, hot rods, marine engines, and high-performance builds. This thermostat switch automatically regulates when coolant circulates through your system, protecting your engine from overheating while maintaining optimal operating temperature. Whether you're upgrading an existing cooling circuit or building a custom setup, this automatic switch provides reliable temperature management without manual intervention.

This automatic thermostat switch engages at 180 degrees Fahrenheit and disengages at 165 degrees, creating a stable operating window that prevents thermal cycling while minimizing stress on engine components. The switch features dual 8 AN inlet and outlet ports with 1/2-inch male barb fittings, allowing seamless integration into hose-based cooling systems commonly found in custom and performance applications. The compact design—measuring just 2.7 × 1.35 × 3.75 inches and weighing only 0.18 lbs—fits easily into tight engine bays without requiring extensive modifications to existing plumbing.

Engine builders, restoration specialists, and performance enthusiasts benefit most from this automatic thermostat switch when designing closed-loop cooling systems for street rods, drag racing vehicles, and custom watercraft. The 8 AN barb fitting configuration ensures compatibility with modern high-flow cooling hoses and works effectively with both mechanical and electric water pump setups. Installation requires only basic hose routing skills—simply position the switch in your return line where coolant naturally flows, connect your hose barbs, and secure with quality hose clamps for years of reliable temperature control.