Engine Fan Thermostatic Switch for all Military Humvees

Thermostatic engine fan switch.  215 DEGREE FAN DRIVE THERMOSTATIC SWITCH FOR ALL HMMWV MODELS, 6.2 OR 6.5.  Part number 12338599.  NSN 5930012377322

Thermostatic Switch To Control Engine Fan for HUMVEE, HMMWV .  Replaces Factory Part # 12338599.  This Is Not Cold Advance Thermostatic Switch. The function of this switch is to signal the hydraulic fan clutch to engage and cool the engine down.

The 215-degree rating means the temperature threshold where the switch activates or deactivates to control the engine cooling fan.

How the Switch Works

• Activation Temperature: At around 215°F to 220°F, the internal contacts in the switch change state.

• Engaging the Fan: On HMMWV models, heating up to this trigger point cuts power to the fan clutch solenoid (acting like unplugging it), which engages the hydraulic fan drive to cool the engine.

       Disengaging the Fan: Once the coolant temperature drops back down to a normal level (usually around 180°F to 190°F), the switch resets, restores power to the solenoid, and lets the fan spin freely again