Miller 244039 Coolant Temperature Switch N.O.

The Miller 244039 is a normally open coolant temperature switch engineered for Mitsubishi engine applications. Its role in the cooling system is precise and non-negotiable: it monitors coolant temperature and closes the circuit at 111°C, triggering downstream components — typically electric cooling fans or dashboard warning indicators — that protect the engine from sustained high-temperature operation. As a direct OEM replacement, it's the right solution when the factory switch has failed, is reading incorrectly, or has degraded to the point where the cooling fan is no longer activating at the correct threshold.

The switch is a normally open (N.O.) type, meaning current does not flow through it under normal operating temperatures — only when the 111°C activation point is reached does the circuit complete. Installation follows standard coolant switch procedure: drain sufficient coolant to prevent spillage, remove the old switch with the correct socket size, apply thread sealant as specified in the service manual, and torque to spec. There are no adjustments to make and no calibration required — the activation temperature is factory-set. Longevity depends on coolant system maintenance; a clean, properly inhibited coolant system extends the service life of any temperature-sensing component.