Old-Bugga wrote:
Noticed the other day that my fan was on, even though I had only done a short trip. Seems to be on all the time? Engine off and cold, I can turn the fan and feel slight resistance from the viscous fluid. Weather has turned cold here of late, so is the fluid more viscous/likely to engage. I don’t really understand the reasoning behind the viscous fan. Up until now, I understood, coolant got too hot, switch brought fan into play. Anybody care to explain?
Sent from my iPad using Tapatalk
The thing isnt perfectly frictionless, so its always going to be spinning if the engine is spinning. Before the clutch is engaged the fan is spinning at some speed less than the pulley in hopes that it reduces the load on the motor. When the viscous clutch engages then it brings the fan's RPMs more in line with the pulley RPM and starts to move more air but also draws more power.
The only way you will have a fan that doesnt always spin is if its electric and its not physically connected to the engine.