Several things can cause this:
Any one of these - or a combination of two or more - can cause the AC to blow warm air.
This means your Jimmy is pregnant with a Jenny.
That is exactly how a heat pump works in heating mode are you sure it's not a heat pump?
why does ac blow warm air? why does ac blow warm air?
Kinda, but it'd be real inefficent and expensive. Think about it: at one end of the room you have the AC making cold air. At the other end you have the fan, blowing that cold air out of the room. Means the AC has to take in new warm air from the outside and cool it. You're better off having a large portion of the air in the room recirculating. That way the AC doesn't have to work that hard.
low on freon
heater on at idle and will not blow warm air. when moving it blows the warm air from the vents. what will cause this
It's due to your car not having freon go and get it charged. The cold air is from you driving!
Your engine is hot.
a long time
whatta?
Are you referring to automotive air conditioning systems? It could be a faulty compressor. It could also be a malfunction of the air door, which mixes air from the heater and air conditioning to provide finer temperature control.
Hire a fix-it guy?