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Miller 244039 Coolant Temperature Switch N.O. — main product image
Miller

Miller 244039 Coolant Temperature Switch N.O.

OEM-spec normally open coolant temperature switch for Mitsubishi engines, activates at a precise 111°C to protect against overheating.

$326.99*
✓ In Stock on Amazon.com
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*Price sourced from Amazon.com. Last updated:Jul 14, 2026.Price and availability are subject to change.

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Overview

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.

Key Features

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Specifications

Brand
Miller
Part Type
Coolant Temperature Switch
Operation
Normally Open (N.O.)

Pros & Cons

👍 Pros

  • Fixed 111°C activation point matches Mitsubishi OEM specification precisely, ensuring correct cooling system trigger behavior.
  • Normally open design is the correct circuit type for factory cooling fan and warning light circuits on compatible applications.
  • Direct OEM replacement simplifies sourcing — no modification required for compatible Mitsubishi engines.
  • Miller is an established supplier with a track record of OEM-grade parts.

👎 Cons

  • Fitment is specific to Mitsubishi applications — universal listing means confirming thread pitch and connector compatibility is the buyer's responsibility.
  • Minimal packaging documentation means consulting the vehicle service manual for torque spec and sealant requirements is essential.
  • Single fixed activation temperature — not suitable for applications requiring an adjustable threshold.
  • Not compatible with propane or LP without noting this is purely a coolant circuit component — no field adjustability.

Frequently Asked Questions

This switch is listed as compatible with Mitsubishi engines. Verify fitment against your specific year, make, and model using the Miller parts compatibility chart or your vehicle's service manual before ordering.
A normally open (N.O.) switch completes the circuit only when the activation condition is met — in this case, when coolant temperature reaches 111°C. Below that threshold, the circuit remains open (off). This is commonly used to trigger cooling fans or warning lights at a set temperature.
The switch activates at exactly 111°C (approximately 232°F). This fixed activation point is set at the factory and is not adjustable.
It is designed as a direct OEM replacement for compatible Mitsubishi applications. Confirm thread pitch and connector type match your existing switch before installation, as variations exist across model years.
Typically a deep socket or crow's foot wrench matching the switch's hex size, thread sealant tape (if not pre-applied), and a drain pan to catch coolant lost during removal. Allow the engine to cool fully before starting — hot coolant under pressure is dangerous.

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