The description is a little vague. If it's an AZC (dual zone), check fault codes by holding the AC and Recirc buttons for 3 secs an turning the temp knob a click. Verify that the A/C compressor is turning on when you expect it to by watching the clutch under the hood. Ideally you'll want to have a set of pressures for the high/low on the A/c. If the compressor isn't engaged when the a/c is turned on, try tapping the front with a rubber mallet to see if the clutch engages.
2004 Imola BMW ZHP
2006 Commander Limited Hemi QD2
"Bought, Not Built"