Air started blowing hot air all of a sudden.

Air started blowing hot air all of a sudden, someone checked it and said compressor is coming on and pipe is cold. The hot air comes thru all the vents makes a whitsle or whining noise in the system area. Cannot control temp thru system at all, except heater blows I can change the volume but not the temp. Now hot air is burning up my feet as though it is engine heat coming into the floor board everytime that happens the noise is present. I was told something about a clutch door that is not shutting. Need to get this fixed immediately. The allergy season is here. HELP