International 4900 Cooling fan

Air clutch fan or viscous fan?

 

With the engine off will the fan rotate by hand without turning the fan pulley? There will be drag but it should turn.
If not, it is seized. Replace the fan clutch. Quite common.

 

Put shop air to the air line to release the fan clutch and try to spin it by hand to make sure the clutch actually disengages. If not, it is seized and needs replacement. If it does disengage, then the solenoid could be bad or something like the ac or another temp sensor is keeping it on all the time which would require further testing.

 

My reply was for a viscous fan clutch. Follow @Heavyd advice.

 

Wire diagrams for your year are only in actual books, I am off work right now, so I can't look it up. Normally, there is 12volts supplied to the solenoid to shut the fan off. If you jump 12 volts to it and fan shuts off (releases) then you know the solenoid is good. Power for the solenoid will come from a fuse, and typically go through the temp switch. When the engine gets hot enough, the switch opens which kills power to the solenoid to turn the fan on. So you might have to become a detective, and follow the wiring to see where it goes. I think you are on the right track with that temp sensor that is unplugged.