Horton DM 2 speed fan drive

Anyone on here have experience with this unit? It's an "eddy current" drive on low speed and then it locks up like a regular fan clutch when needed for additional cooling. My question is: Does this fan drive ever shut completely off when not needed for cooling the engine or A/C system? Or, when the engine is running does it operate continuously on the eddy drive, locking into high speed only when needed?

 

Thanks. I thought perhaps the magnets were electromagnets that relied on a signal from the ecm to activate them. Makes me wonder why they are not.... Back in the late 80's there were fan clutches available that did use electromagnets. I thought they were great -- nothing to wear out or slip like a clutch disk. Cummins bought 'em out and they've not been seen since.

 

It was a Facet brand fan drive. There was no mechanical connection other than the bearings on a common shaft between the fan and the hub assembly. There was an electromagnet that when engaged caused the fan to spin at the speed of the shaft on which it was mounted. Engagement was gentle in comparison with a clutched drive like a Horton, with no violent torque spikes. I had several of them on early Detroit Series 60's in Freightliners. They weren't modulated to operate at varying speeds, just off and on. I was really happy with them. No failures at all.