Mine recently failed, its supposed to run all the time, worth checking the fuse? With mine the motor had burnt out making the fan very intermittant and never running very fast so I had to replace the entire fan - its quite pricey (£240) easy to replace without removing much, little screw on the top, twist fan then take it out, have to remove timing belt covers for access and the cables are annoying as they run below the viscous fan and then plug into the connector by the power steering fluid tank. with a bit of fiddilling it can be done without removing bumper or putting car in service position.
Initally i removed the old one and realised the bolt that holds the blades in place was loose and after tightening it worked for 2 days, I think the bolt worked loose beucase it was failing & vibrating loads.
