Thread: cat fan clutch

thanks for the info, all of what you said sounds completely plausible. I'll get it checked out, I assume this truck has had this problem a while because when I bought the truck about 3 months ago the fan clutch was slipping, I had my local mech put a new clutch on it, but i didn't know the thing was kicking in and out like this until I hauled a load with it and got it up to operating temp. I...

i also hear a faint clicking noise under the dash like a relay or breaker clicking in and out, and i can turn the manual toggle switch on and it locks in good, i'm with you probably a bad switch but i was just kind of wondering what controlled the switch so i could know what i was talking about when i went to the shop

Check the fan clutch relay and also check the solenoid that engages the fan also with time they wear out and cause slipping in the clutch also. If you are running your AC however what you are hearing is normal since if your compressor gets high on pressure it calls for the fan to run to reduce them.

There is also a parameter that can be set in the ECM for the amount of fan on time. Any authorized shop with the ET tool can set this for you.

sounds like a bad switch. have a shop look into it.

Can set duration for ac operation. we normally set to 60 seconds so fan doesnt cycle as ofton. Is thermostat good. could fan be on because tstat no opening and running all time to keep cool?

After replacing the A C compressor on my truck, I mistakenly put a little too much R134 (lost count of the cans). This caused the high pressure switch to cycle the fan constantly, just as you mentioned. If you hadn't added any refrigerant lately, the high pressure switch could be faulty, and causing the constant cycling.