wish to second larry b's. opinion. check belt tension, belt tensioner and damper. replace if necessry.
another area to look at is any slippage of the clutch. again
if oily, clutch will not engage. the fix for this problem
is a can of engine degreaser. spray and rinse clutch area.
also, check sensor on top of compressor. there are two
screws on it. tighten these if necessary. good luck.
you need your a/c working to dehumidify the cabin air
this winter. otherwise, all windows will fog up. this
is a safety issue, especially if driving in the freeway.