Cat 3406e fan staying on

How long has it been on? I am sure this is killing your fuel mileage.

also did you wash the engine recently?

 

And you haven't replaced the clutch? I am going to guess a clutch. I would be very weary about that fan hub also. If you have been running the truck for three months with the fan on I would be checking for bearing play on the hub.

 

I agree, it's the high pressure A/C switch.

 

Well yes it could be and it is probably wise to check it before you buy a clutch. Someone else may know the answer to this but it seems like you could take the wire off the switch and take a little piece of wire and jump it. If you fan turns off then it is you high pressure switch.

 

On my 03 pete; If I disconnect the A/C high pressure switch, the fan will engage. When I jump the switch the fan will disengage. I just opened the hood and tried it.

 

thats what I did. The A/C system has 2 pressure switches, a low pressure and a high pressure. On my pete the high pressure switch is located on the radiator in the hose going from the compressor to the condenser ( the condenser is in front of the radiator)

 

The high pressure switch should be in the smaller diameter line.