Excessive engine fan cycling

[Matt]

I'm having trouble with the fan having random 'fits' of where while going down the road the fan will start cycling on for 30 to 60 seconds then off for a second and then back on. It'll do this a few times and settle down. It seems to be triggered by acceleration up a small hill in the road bit not every time. Temps are totally normal at 185 coolant and 230 oil. It's on a 08 kw t660 with a isx871 with MM. The only other thing to mention is that the ac system sprung a leak and is discharged at the moment. This didn't start when it discharged though. Any ideas on what to look at?

[axe]

(03-02-2017 )Matt Wrote:  I'm having trouble with the fan having random 'fits' of where while going down the road the fan will start cycling on for 30 to 60 seconds then off for a second and then back on. It'll do this a few times and settle down. It seems to be triggered by acceleration up a small hill in the road bit not every time. Temps are totally normal at 185 coolant and 230 oil. It's on a 08 kw t660 with a isx871 with MM. The only other thing to mention is that the ac system sprung a leak and is discharged at the moment. This didn't start when it discharged though. Any ideas on what to look at?

Low Freon will make it cycle, AC high pressure switch bad will, along with air leak at fan clutch or air line feeding it, as well as the solenoid. On our Pete it was dirty connection on high pressure switch. Hope that helps.

[in2trux]

Check the fan solenoid. Air leaks or bad electrical connection, very common problem with Paccar.
Default is fan on.

[BLOODSWEATTEARSMX13]

Same happened to me. Had a bad wire from the AC compressor that had to be replaced. Lost the hub fan clutch before I figured it out. If it is kicking on and off the hub fan clutch will fail premature. As I recall the clutch was a $600 part so find the short asap. Good luck.