Hard to say with any precision, I am assuming the blower is blowing air, just not cold air? In that case I would say you are still low, as just the clutch engaging does not mean it is charged well enough to cool, but enough to run the comp. Do the hard lines under the hood get frosty cold with the compressor on? If they are cold then so should be the airflow. If they don't get cold, it is too low, or there may be a clog in the system.