Cooling fan engages when taking off from a stop

[Fordracer]

I have a 6.4 that most of the time when you take off from a stop the fan is engaged for a little while. I monitored the fan pids while driving and when you let off the throttle and coast for about 4 seconds the fan duty cycle goes to 74.6% for about 2 seconds and then when you accelerate the fan is engaged for a little while and will go over 2,000 RPM. The coolant, oil, and trans temperatures are well below what will turn the fan on and the A/C is off. What could trigger the duty cycle to come on while coasting? I've never noticed on 6.4's but I know 6.0's turn the fan off at idle so I don't understand why the 6.4 is, especially when the temps are low.

[lmorris]

Could just be self testing the fan clutch. I didn't think the 6.4L did this, bit maybe.

[cbriggs]

Check the AC pressure pid too. Even though it is off, high pressure can make the fan run I believe. Could have a circuit issue that is triggered by decel?