patrol tb42 e fan clutch runnimg very often

[MudRunnerTD]

G'day Larry,
really, really dumb question.
What starts/triggers the fan? Is it a thermostat/sensor of some kind? If so could it be that that is cactus?
If it automatically runs when the radiator cap thermostat opens (which sounds reasonable for a 'viscous' unit) then maybe that's operating at the wrong temp..
As I say a bit dumb but what the....
Col.

Not a dumb question at all mate but the answer is that the viscous fan has a heat sensitive spring in the centre of it, when the spring heats to a set temp it expands and compresses the fan hub and it engages.

The fan will spin all the time but without load, when it engages you can hear it load up and spin harder until the engine cools below the trigger point then it lets to as the fan spins without load again.

[Col.T]

Thanks Daz.
on that basis it looks as if the fan itself is cactus 'cause if it was O.K. it wouldn't engage when the motor's cold.
What else could it be?????
Col.

[Bloodyaussie]

Those fans always engage at first when cold and as you drive off they disengage.

They can stuff up either way.. I have had them lock on and its like driving a truck and I have had one that would not come on at all...

[Dales300exc]

A mate had 3 dud viscous hubs they were brand new. Either try another or buy genuine.

[huardlc]

yes thats right. and no Col, its not a stupid question. if we all knew everything, we will probably be doing something else...bloody is right. its the oil inside the fan(clutch) that makes contact and locking it up.i think the heat is transmitted via the little strip of metal in front of the clutch itself.
the problem i hve is that it starts even with very cold engine. and yes bloody, i dont think its genuine nissan.