2588342C91 | Genuine Horton® 2 Speed Fan Clutch

Compatible Vehicles & Engines

Part number serves as an OEM fitment for medium- and heavy-duty International / Navistar trucks equipped with high-horsepower diesel engines:

• Heavy-Duty Highway Trucks: International ProStar, LT Series, LoneStar, RH Series.

• Vocational & Severe Duty Trucks: International WorkStar, HV Series, HX Series, PayStar.

• Compatible Engine Platforms: Navistar N13 / A26, MaxxForce 11 / 13, and Cummins ISX15 / X15 diesel engines.

1. What is it?

Part is an OEM Horton® DriveMaster 2-speed fan clutch mounted between the engine crankshaft pulley and the cooling fan blade. It dynamically controls the rotational speed of the radiator fan based on real-time engine cooling demands communicated by the Engine Control Module (ECM).

2. Core Functions & Operation Modes

• OFF Mode (Disengaged): When the engine is cold or under low thermal load, the fan stays disengaged, saving horsepower and reducing fuel consumption.

• Low Speed Mode (Eddy-Current Drive): For minor cooling demands (such as light air conditioning load or mild ambient temperatures), the fan engages at a reduced speed using magnetic eddy currents. This provides quiet, low-power cooling without fully locking up.

• FULL Speed Mode (Full Air Lock): When high engine coolant, intake manifold, or transmission temperatures are detected, air pressure fully locks the clutch, spinning the fan at maximum engine RPM for maximum airflow.

• Benefits: Reduces overall engine noise, extends fan belt life, improves fuel economy, and reduces drag on the engine compared to single-speed clutches.

1. Engine Overheating Under Heavy Load or Long Incline

• Symptom: Coolant temperatures quickly spike into the red zone when hauling heavy loads or climbing hills.

• Cause: The clutch fails to engage into Full Lock Mode due to air seal leakage, insufficient system air pressure, or worn friction discs that slip under torque.

2. Fan Constantly Engaged at Maximum Speed (Stuck ON)

• Symptom: Extreme fan roar, loss of engine horsepower, and noticeable drop in fuel economy at high highway speeds.

• Cause: Loss of control air pressure (default failsafe mode locks the clutch ON), a failed air solenoid valve, or mechanical binding/bearing seizure inside the clutch hub.

3. Failure of the Low-Speed (Eddy-Current) Mode

• Symptom: The fan stays completely idle during low-cooling demand scenarios (like idling with A/C on), causing poor A/C performance or sudden, harsh transitions straight into high-speed full lock.

• Cause: Electrical failure of the electromagnetic coil circuit or corrosion/damage to the internal eddy-current drive plates.

4. Excessive Air Leaks from the Fan Hub

• Symptom: An audible continuous air leak from behind the cooling fan when the engine is running or when air pressure builds up.

• Cause: Worn internal air seals or damaged air-cartridge seals inside the Horton shaft assembly.

5. Mechanical Noise & Vibration (Grinding or Squealing)

• Symptom: Loud metallic grinding, squealing, or front-engine vibration that increases with engine RPM.

• Cause: Worn internal ball bearings or dry friction material causing metal-on-metal contact.