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Modulator Variable-Speed Retrofit Packages

Fan Drive Retrofit

Modulator Retrofit Package

Variable-Speed Retrofit Packages

Prevents Under- and Overcooling in All Climates

From Alaska’s North Slope to the Gulf Coast and any climate in between, you’ll get better engine and cab temperature control by replacing your on/off fan clutch with a Modulator Variable-Speed Retrofit Package.  Modulator and your truck’s engine control module (ECM) work together to manage fan speed on heavy-duty line-haul and severe-duty vocational trucks, where on/off fan clutches over-cycle or do not provide optimum performance.

  • Prevents under and overcooling in all climates
  • Faster cab warm-up, more efficient air-conditioning and quiet, modulated fan speed for improved operator comfort
  • Maximizes engine power to the vehicle drive wheels
  • Improved fuel savings in most applications
  • Long service life under severe duty and reduced downtime


Two Modulator retrofit packages are available. Visit the links below for application and part numbers information.


For specific Cummins engine applications, the retrofit package contains: 

Retrofit packages for applications that do not require the Horton Di controller use the vehicle ECM to directly control the Modulator.

Modulator Fan Drive assemblies include application-specific pulleys and mounting brackets, paired with rugged WindMaster HS11 fully molded fans for maximum efficiency. Everything needed for plug and play installation is engineered into the retrofit installation kits. See the product selection table for details.