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Fan Drives

Fan Drive or Fan Clutch

Fan Drive (or Fan Clutch)

The purpose of a fan clutch with a mounted fan is to help ensure that engines do not exceed certain operating temperatures, which are usually set by the manufacturer. The temperature is detected by a bimetallic sensor system or by an electronic control. The two terms "fan clutch" and "fan drive" are interchangeable.

Although the fan clutch is driven by the engine, it is designed to stay "idle" in off mode and to turn on (with the engine as the primary force) as the engine temperature increases. There are three basic types of fan clutches, each of which offers various advantages in terms of function and price: automatic clutches, two-speed clutches and variable-speed clutches.

On/Off Fan Clutch
DM Advantage On/Off

On/Off Fan Clutch

Essentially, a fan clutch with automatic changeover turns on when the engine reaches a certain temperature. It then remains switched on until the temperature drops back into the optimum range -- hence "automatic changeover".

The fan clutch with automatic changeover is the simplest of the three types and usually the least expensive solution. It is widely used in Class 5-8 trucks, buses and some off-highway applications. It is important to match a fan clutch, if possible, to the particular application, as the model could run continuously due to incorrect application. As a rule, the fan clutch should not be switched on more than ten percent of the time. Although continuous operation is not a problem (apart from a reduced lifetime), the load on the engine increases fuel consumption -- and noise increases during constant operation. Ultimately, the power consumed by the fan clutch reduces the power available to the vehicle.

Horton offers a variety of auto-shift models to meet the needs of on- and off-highway products. These include DM Advantage®, EC450 / EC600, HT / S Advantage and HT650.

Two-Speed Fan Clutch
DM Advantage Two-Speed

Two-Speed Fan Clutch

A two-speed fan clutch is a good choice for applications in which the fan must run more than 10 percent of the time to cool the engine. The two-speed fan clutch can shift from a lower eddy current mode to a higher spring-loaded mode for optimal cooling. It is ideal for heavy commercial vehicles, but is also used in some on-highway areas. Typical applications include garbage trucks, concrete mixers with a rear engine, dump trucks, etc. In general, two-speed fan clutches are well suited for vehicles that are not constantly in motion or are stationary, so that no air pressure flows back through the engine. The two-speed concept is aimed at limiting the number of fan clutch interventions necessary. Accordingly, it reduces fuel consumption and noise and provides more power for the vehicle in eddy current mode.

Two-speed fan clutches typically cost more than on/off fan clutches but are the preferred drive for  some specific applications. They also offer shorter warm-up times in cold weather, less wear due to fewer cycles and longer life.

Horton offers a variety of two-speed fan clutches for on- and off-highway applications, including DM Advantage® and Arctis.

Variable-Speed Fan Drive

Variable-Speed Fan Drive

Variable-speed fan drives usually feature viscous, or fluid, technology. In general, a variable-speed drive operates in accordance with the cooling requirements to maintain the engine at an optimal operating temperature. When less cooling is required, it operates at a low idle speed, allowing for faster warm-up times, higher internal temperatures, significant noise reduction, more available power, and lower fuel consumption. As more cooling is required, it accelerates faster, smoother, and with less stress on the drive, motor, and adjacent components. It is also maintenance-free (no friction liner) and helps OEMs meet Tier 4 requirements. Variable-speed operation also helps reduce fan abrasion from dirt, stones, and other debris as the fan clutch operates at lower speeds and runs fewer and shorter cycles.

Variable-speed fan clutches are available in a variety of sizes for a variety of applications, including medium- and heavy-duty trucks, commercial vehicles, buses, specialty off-highway vehicles, and many off-highway applications