LO 11-7 Identify and describe the types, features, and applications of cooling fans

LO 11-07: Identify and describe the types, features, and applications of cooling fans.

Variable-Speed Engine Fan

To reduce parasitic loss caused by an operating cooling fan, many late-model MD and HD engines use a variable-speed cooling fan Figure 64. Operation of the fan is controlled by the engine ECU using a PWM signal to the clutch coupling mechanism to control the fan speed. An electrically operated control valve is used instead of the bimetallic, heat-sensing spring used in conventional viscous cooling fans. Slower fan speed also translates into less engine noise.

FIGURE 11-64: An electrically controlled, variable-speed engine fan reduces parasitic power loss and provides optimal control of fan speed.

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