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?