Engine fan

[Stevev]

Hey Guys
Happy Thanksgiving
this may be a dumb question but
should I be able to turn the fan blades when the engine is off?
blades don’t spin when it’s off or when it’s running and engine is cold or at 160
degrees?

 

[Andyrv6av8r]

Correct. Fan should freewheel anytime it's running.

 

[Stevev]

Let me clarify
the blades don’t freewheel
and when it’s idling it spins at the speed of the pulleys when the engine is cold or hot

 

[Andyrv6av8r]

Let me clarify the blades don’t freewheel
and when it’s idling it spins at the speed of the pulleys when the engine is cold or hot

Completely normal. When I say " freewheel ", I mean it spins along with the engine due to friction and not the same speed as the engine as if it was engaged. If you have ever seen a 939 series 5 ton engine running with the hood up, the fan normally does not turn at all unless it's engaged.

 

[98G]

As I understand Steve, the fan is locked and turning with the engine at engine speed when the engine is running. Not being carried along by parasitic drag. Not "completely normal". Fan is engaged when it shouldn't be.

And unable to turn by hand when the engine isn't running.

 

[Andyrv6av8r]

Have you unplugged your time delay module with the hood up, engine idling, to verify that the fan clutch is working?

Watch this video.

https://youtu.be/mfAG4rV-7Nk

 

[TOBASH]

SOOOooo, if I want the fan to disengage while water fording... Rather than rev the engine I can install a switch between the thermoswitch wires. Then flip the switch to ON when I want the unit to disengage for water fording. Nice.

Great video.

T

 

[Retiredwarhorses]

SOOOooo, if I want the fan to disengage while water fording... Rather than rev the engine I can install a switch between the thermoswitch wires. Then flip the switch to ON when I want the unit to disengage for water fording. Nice.

Great video.

T

i have been installing fan cutoff switches like this for many many years....

 

[papakb]

When I first got my truck years ago it had the normal set of fan problems and I installed a switch along the left side of the dash with a 3 way switch on it that allows me to operate either in always on, always off or normal cycle modes. It's a simple wiring change to the TDM.