Ford Repair: 1999 ford expedition ac repair, compressor clutch, ac repair

Question
I have 1999 ford expedition and the ac will cool good but then it will start blowing out hot air.  Can you help me, i tried gasing it up but that didn't change it. Could i have be doing it wrong."

Answer
need to know when it is not cooling is the compressor clutch engaged-if not you could have a bad cycling switch or the airgap between clutch drive plate and pulley may be to wide-try running it until it quits cooling then check driveplate on front of compressor it it is not turning tap it with a hammer or wrench and see if it engages if it does you will need to pull off front pulley and remove a shim or take one out and put in a smaller one-if it don't check power and ground on front clutch if you have both and not engaged you have a bad clutch coil. follow up. mark