ac compressor cycling 02, 4.3

Out changing the oil this morning, noticed that the A/C compressor was cycling on and off, gauges were set at full heat. Any clue why?

If cold weather and cold engine it may cycle on and off some.
The ac runs on defrost mode to help dry off windows.
How often was the cycles?
Check it after it warms up to good and hot.
MT

MT-2500 is right. If the heater controls were set to defrost, by design the AC compressor will cycle to dry the air to assist with defrosting/defogging the windshield. Almost all newer cars have this "feature". I personally would like to have control of the compressor regardless of where my controls are set and not have the car be "smarter" than me. Oh well.