Fan Clutch

[tugboatphil]

What's the deal with this clutch? From what I can tell, my fan runs all the time. Is it not supposed to? If not, what is the benefit, and is there any adjustment to make it work?



Thanks.

 

[Greenleaf]

I don't know... ... ... ... ... .















What kinda clutch is it? The original will "sense" the temp from the radiator and "turn on" or engage when it's hot enough. You don't need a power robbing fan when the truck is at high way speeds and they seldom engage while setting in traffic. They will however, always turn a % of engine speed as it is needed to pull some air through for the ac condenser. When one is fully engaged... . it sounds like a RR locomotive. I'd bet you $, you are seeing it only turn a % of capacity.



-S

 

[tugboatphil]

I know I'm setting myself up here, but can you actually hear this engage while driving?

 

[bgilbert]

Phil, its not a Horton or other electric fan, its belt driven so its gonna 'turn' all the time. Just it should only 'engage' as Scot said when its hot enough. It be nice to have a Horton setup. To check the clutch, check when truck is cold and off. The fan should rotate freely with little to no resistance, try rotating it with hands. If its tough to rotate its shot, meaning locked up or engaged all the time. Don't check when warm cause a locked up clutch will turn freely when warmed up.

I think what its doing is, its not spinning as fast as the pulley and engine speed is spinning, when radiator temps are cool. Once it reaches a certain warm temp, it will sense this and lockup/engage and spin the same speed as pulley and increase with engine speed... does that sound right? Didn't Scot just say that...

 

[Greenleaf]

I dunno. How's yer hearing?



You would be driving along. Some hot day. Pulling a 4% grade for like 10 miles. Hoofing, oh, I'd say , 19K behind the truck. Then, you would notice a loud roar from up front.



Hows that?



-S

 

[bgilbert]

I know I'm setting myself up here, but can you actually hear this engage while driving?

They say you can, but I don't think I've ever heard mine, new clutch too. Maybe I've never worked my truck in the summer too much, plus loud truck and stacks. Now in big trucks with electric fan or clutch setups, I sure hear the fan kicking on, roars like a freight train.

 

[JJump]

I just returned from a 4000 mile trip from St Louis to Coeur d'Alene ID towing my 30 ft 5th wheel (unloaded wt 7100, combined wt 13,700). I drove pretty steady, 55-58 mph range using cruise control. Ambient temps were in the 50-70 deg F range. I could hear my fan engaging & disengaging quite often in both the flats & in the hills. The engagement/disengagement lagged behind the load by 30 seconds or so, but it didn't necessarily follow the coolant temp gage in the dash.



This was a question I wanted to post to the forum. I guess you could call this a timely return!

 

[tugboatphil]

Bill,



Thanks for the explanation. I guess that's what Scott was trying to say, but I didn't have my English/Buckeye dictionary!

 

[MrWinkey]

I can get mine to lockup when the AC is blowin Ice headin up a pass @ 70.



First time it did it was this last week I was on vacation 95+ deg out here and I hear this big WHRRRRRRRRRRRRR Granted I only had 1200 pounds in the bed so it wasent too bad.



After a second of panic I realized what it was. First time for the both of my trucks... . never had the fan kick on before.....

 

[Dfeland]

The book says to test the bi-metal spring by prying it out of its seat and rotating it. and if it rotates more than 1/2" than the clutch is bad. Also at with an abient of above 70 or so there should be alot of resistance to the fan by turning it. The fan should run near engine speed otherwise your a/c will not work. But as the engine speeds up the fan will stay at a lower RPM until lockup occurs with with bi-metal. Our fans are actually two units. A viscous drive and a thermal drive, the viscous keeps it a certain rpm at idle and than when the engine gets hot the bi-metal reacts and locks the fan up for direct drive.

 

[mdatc]

If in doubt, replace it!!! I just replace mine. I can hear it kick on about the halfway mark on the temp gauge. It sporadically kick on/off before. Didn't check the bi-metal spring, but there was reseudial oil stains around the inner core. It just time for a fan clutch change.