Thread: Viscous Fan Information Needed.

The viscous fan clutches I have had a play with are fitted with a spiral bi-metallic spring on the front. This moves the small shaft that controls the fluid flow inside. So you can unship the spring out of its slot, and manually move the shaft to either lock or unlock. You can also test the bi-metallic spring movement with a small gas torch. I bend the spring hook end on certain hubs to lower the cut-in temperature as I want a slightly cooler running engine than stock.

So to summarise, your clutch could be stuck either on or off due to a control shaft fault.

Without a copy of RAVE at work – what controls the clutch, surely it can’t be a thermo spring?

When I start leave in the morning the fan runs for about 1 minute and then cuts out if the AC is not on. If the AC is on the fan stays running even with the engine stone cold. I hate the extra noise of the fan especially when the engine doesn't need it.

Originally Posted by harlie

Without a copy of RAVE at work – what controls the clutch, surely it can’t be a thermo spring?

When I start leave in the morning the fan runs for about 1 minute and then cuts out if the AC is not on. If the AC is on the fan stays running even with the engine stone cold. I hate the extra noise of the fan especially when the engine doesn't need it.

Harlie, I think Gav means the engine driven fan, the electric "Auxilliary cooling fan" is the electric one, the reason it comes on with the aircon is to keep the pressures down in the aircon system by minimizing the condenser temperature. That's on my "to do" list as mine never comes on!

I recall seeing a pic of a modern viscous fan on an engine with an electrical connection. ECU controlled on your vehicle?

yeah it must, I'm talking about the belt driven fan - on mine it runs when the ac is on no mater what the engine temp, it's the one that makes all the noise, looks like some reading tonight. I've not checked the aux fan, maybe that's my problem.

Originally Posted by bee utey

I recall seeing a pic of a modern viscous fan on an engine with an electrical connection. ECU controlled on your vehicle?

I don't think so - I know they use these on some small trucks - Borg Warner make one, but when I looked up to purchase a new one, it looks like a plain old fashioned viscous. It doesn't seem to have a spring on the front, everything must be internal. This link to flea bay shows some photos - RANGE ROVER L322 3.0L DIE VISCOUS FAN COUPLING ASSEMBLY | eBay

Cheers - Gav

Originally Posted by bacicat2000

I don't think so - I know they use these on some small trucks - Borg Warner make one, but when I looked up to purchase a new one, it looks like a plain old fashioned viscous. It doesn't seem to have a spring on the front, everything must be internal. This link to flea bay shows some photos - RANGE ROVER L322 3.0L DIE VISCOUS FAN COUPLING ASSEMBLY | eBay

Cheers - Gav

It's still a bimetallic spring, it presses inwards instead.




[ame="http://en.wikipedia.org/wiki/Fan_clutch"]Fan clutch - Wikipedia, the free encyclopedia[/ame]

if your ac fan runs anytime that the engine does then at some point your ECU has logged an overheat fault, one of the first things it does is manually trigger and lock in the fan control to attempt to get you some airflow. (IT does help I did a heap of experimenting with one of my V8 discos in ambients below 25ish degrees with the AC turned off an manually run the AC fan is enough to keep the engine under overheat temps without an engine fan even in mild stop start traffic.)