[Johnny B]

Well, I'm not really sure how to start. You are kind of all over buddy. Some of what you are saying makes total sense, some doesn't follow at all. I'm going with the possibility you are just making some coincidental observations, because if all you have stated is correct your car has a ghost. Every car made in the last 20-ish years turns on the AC when the HVAC system is set to defrost. With that when ever the AC runs the computer forces the radiator fan to run, regardless of ECT.
I believe the problem is a bad resistor pack for the radiator fan motor, unless you can provide us better information this is where I would start. Since this is a non-replaceable part, you will need to replace the whole fan assembly.

This video is the best one I have come across for explaining your issue.

 

[ChevyGuy]

I'd check to make sure the pressures in the A/C system are correct. If the high side gets too high (overfill?), the fan will be commanded to go to jet mode. And yes, the A/C runs in various modes including defrost.

If it was a problem with the resistors, I'd expect the fan to cycle between high and off.

 

[Kal]

I'd check to make sure the pressures in the A/C system are correct. If the high side gets too high (overfill?), the fan will be commanded to go to jet mode. And yes, the A/C runs in various modes including defrost.

If it was a problem with the resistors, I'd expect the fan to cycle between high and off.

Been a while since o have posted. Replaced the AC condenser, trying to fix the high side pressure problems. Refilled the car to where everything is right but now the fan cycles on and off in jet mode. Jet mode (loud inside and outside the car) 2-3 seconds and off for 5-10. AC is blowing cold. I'm trying to get a video uploaded but can't figure out how to get the site to let me do it.

 

[CHEVYCRUZE RS]

prob just a faulty temp sensor and check your water pump electrical connection for any corrosion