Was having an issue with my AC. It would blow cold just fine for 5 minutes, and then blow hot for 2 minutes and then cold again. Yes, I timed it, and it was pretty consistent. i have no AC test gear so took it to my local experts. Their diagnosis was the fan clutch, which was original with 330k miles. Replaced the fan clutch, and we have cold air all the time now. This is quite useful in South Texa.