Electronic Fan Clutches

Electromagnetic on/off clutches give more control.

Electronic controls give operators and engineers the tools to no longer put up with certain behavior from mobile equipment systems.

For example, the traditional engine and cooling fan combination has the fan spinning when the engine is started. That may not be desirable in a school bus in Ely, MN. On a crystal-clear -20 F winter morning, you don't want the fan to start removing heat before it has a chance to warm the engine as well as transfer some of that energy through the cabin.

That's where Warner Electric's electronically controlled fan clutches have filled a niche. The system designer can program into the engine ECU exactly when the fan should turn on.

The result is an intelligent cooling system. "If you want it on it's on — off it's off," says Kal Vanlaningham, chief engineer, Warner Electric, South Beloit, IL. "The only fan rotation will be due to wind through the radiator when the truck is in motion. If you are parked the fan will be stopped. If you want that fan to move up to full engine rpm, it can be on right away, with no slippage."

Warner Electric has been making fan clutches since 1992. "Our core technology is electromagnetic on/off clutches, typically for medium-duty trucks," says Gary Haasch, product manager, Warner Electric. "We also make fan clutches for other applications, such as refrigeration units for semi truck trailers."

Meeting EPA regulations for 2007 is requiring engines to run hotter. OEMs want bigger fans that will be imperceptible to the operator when it kicks in.

"That can be a disadvantage of the electromagnetic clutch," says Vanlaning-ham, "so we developed Softstart, software that feathers in the engagement of a clutch, allowing it to slip so the operator doesn't feel the fan engaging."