you can look into the sight glass with every thing turned on(air)if you see bubbles,tell her I said hi,no really now,if you see bubbles it is a sign of low charge,if no bubbles it may be empty or fully charged,if empty the clutch should not be engaged,this would mean no cooling.
The best way to be sure about it is to find a Friend that can put gages on the system,this way you are sure of the Freon in the system,just -n-time