Arrived onsite for ac maintenance on 1 system . Changed 12x24x1 filter. Turn AC on to confirm operation. Checked all electrical. Chemically Cleaned outside unit, measured pressures for R22 at 60/90psi with 21 degree sub cooling with outside temperature at 43degrees. Measured temperature drop at 16 degrees. blew out condensate line. Performed efficiency test utilizing MeasureQuick. System running but may be slightly low on refrigerant.