Ok, so a little background. I have a 2002 F150 Lariat, i have owned it since it was a year old. Currently has 158,000 miles. I have never had the a/c checked and never had a problem. Still cools as great as the day i bought it. I have noticed in the past 4 -5 months when i get in and start it, i let it idle a few seconds and then kick the a/c on max. I have the digitial controls. When it starts up, it will blow cold a few seconds, then start blowing warm air. Still blows out of the vent, just warm. If i lower the fan speed manually, it blow cold again. Or, if i rev the engine. It's done this maybe 3 times in 4 months. When it does operate while driving, it still is ice cold. Don't have a thermometer, or i would check the l.a.t. I know i should have it checked. Any idea what i may be headed for? Bad compressor? I had a 97 Firebird that lost a compressor, and it took me 4 tries to get one that would last longer than 4 months.
Thanks for any help!

 

Pretty common, actually. You just need to make additional observations so you can properly classify the symptom.

Check for a busted temperature blend door if you have a loss of control of the temperature. They break and flop around.

If, OTOH, the compressor is disengaging when you notice the rise in outlet temperature, you probably have excessive clutch gap and need to perform a shimectomy.