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Discussion Starter · #1 ·
how do you tell if the fan clutch is working correctly...

also i was told that if i wound the spring one more turn it would lock the fan and ensure that the fan was turning at engine spped...waht does teh sprig do and does this spring tightening trick make sense??
anyone ever do thisor hear of this before??

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Rich
Cocoa Beach, Fla
Team Chevelle #380
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To check operation of a fan clutch there are 3 tools required. A thermometer, a piece of chalk, and a strobe light. A timing lite connected to the coil or spark plug wire works well for a strobe.

With the engine off, put a chalk mark on the fan clutch itself and the drive pulley it is attached to. Start the car, and when the air coming out of the radiator (between the radiator and the fan) reaches about 190°F, the clutch should be locked. Point your timing lite at your 2 marks, to see if they are turning at the same speed or if one turns faster than the other. If they are at the same speed, the clutch is locked. If not, keep waiting. When they are going the same speed, look at the thermometer, and see what the temp is. If it is way up there, the clutch is no good!

HTH
 

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Mark, If the engine isn't running, how is the fan clutch going to sense the air temp and lock up the clutch?

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Leo Paugh
Maryland Chevelle Club #017
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Best way I've found is to pull car in garage, let idle until the engine gets hot and stand in front and listen to the fan. You can usually hear it start blowing and then quit after a minute or so. Pretty noticeable usually since these fans really move some air. Real noisy exhaust might make this impossible though.
 

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In addition to Tom3's method, you can see the speed changes when it cycles and you can feel the air flow change a lot , too.
 

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Discussion Starter · #8 ·
how often do these fans cycle...on and off several times within a minute or once a minute or every several minutes ...and are they either locked or not locked with no in between???

if so i presume any motion when not locked is simply due to frictional forces on the fan?? is that correct??

any one know what the spring does and waht effect tightening it one turn would have??

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Rich
Cocoa Beach, Fla
Team Chevelle #380
[email protected]
www.chevelles.com/showroom/70_SS_454.jpg
 

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The basic design of the clutched fan is when the rad is cold to warm and the enging is not is dire need of cooling the fan pin wheels becuase the spring is cold and is not expanded. When the air flow through the rad is hot enough, say 190-200, the spring expands, locking the fan into rotating with the engine speed. The best way I know of to check if it is working right is just to watch the engine idle. When it gets hot enough you will see/hear the fan cycle up.

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