i have a 2000 blazer ac works but blows cold air for 5 seconds and then blows hot air for about 5 seconds, then repeats .after reading past questions and answers seemed like it should be the actuactor motors gear for the blend door.sure enough gear was broken and i replaced only to have the same results. even after recalibration the cycling sounds keeps going on after the 45 seconds said to be needed.is it the cumpter climate control switch or is the blend motor bad or?

 

check two things:
coolant level and if your oil is milky....
and two, whens the last time you ahd your a/c flushed? bad bushings on ac can cause this they dry rot over time,.