fan stuck on
Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
Here is a way to test for fan clutch operation.
Use a good sensitive 'clamp-on' timing light around any fuel injector cable that will trigger the light.
Aim the light at the fan blades.
When the motor is running up to temperature, watch the blades change speed as the thermostatic clutch dis-engauges and engauges over 5 or more minutes in response to temperature changes caused by the thermostat opening and closeing.
If there is no change in speed the clutch is locked up and may need replacement.
The appearence you should see is a stroboscopic visual effect of motion in time with the sampleing cylinder.
Just moving the fan by hand is not alway a reliable indication.
Use a good sensitive 'clamp-on' timing light around any fuel injector cable that will trigger the light.
Aim the light at the fan blades.
When the motor is running up to temperature, watch the blades change speed as the thermostatic clutch dis-engauges and engauges over 5 or more minutes in response to temperature changes caused by the thermostat opening and closeing.
If there is no change in speed the clutch is locked up and may need replacement.
The appearence you should see is a stroboscopic visual effect of motion in time with the sampleing cylinder.
Just moving the fan by hand is not alway a reliable indication.
Elder User
Joined: Mar 2007
Posts: 695
Likes: 4
Clutch fans never stop spinning as long as the engine is running. The clutch "locks" itself when the heat from the radiator gets to a certain temp range and passes over the clutch. Inside the clutch is a viscous fluid that is temp sensative and changes viscosity depending on temp.
If you are in doubt about your clutch, they are cheap and easy to replace.
If you are in doubt about your clutch, they are cheap and easy to replace.
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4x4Subaru
1967 - 1972 F-100 & Larger F-Series Trucks
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Apr 23, 2004 04:03 AM
