In this study, the effects of malfunctions and problems occurring in the system components of air handling units, which are the main elements of the air conditioning system, on the energy consumption were investigated. Investigations were carried out in 10 air handling units located in 5 different shopping centers of Turkey. The malfunctions and problems that may occur in operation of air handling units were determined and the problems causing the decrease in the efficiency prescribed by the design characteristics were determined. For this purpose, rod-type anemometer measuring the airflow in the air handling unit ducts, propeller-type anemometer, and thermal camera were used to measure air tightness and heat losses in the body structure. Also, the tension control of the belt of the fan motors, which is one of the main components of the energy consumption unit, and the pollution control of the air filter have also been carried out. The flow rate of water circulating in air handling units was determined, and losses were detected by energy and exergy analyses with thermodynamic parameters for summer and winter periods. As a result of the calculations, it was determined that the energy efficiency of the air handling units in the cooling period was 63.7% and the exergy efficiency was 59.6%. The energy loss is 471 kW and the exergy loss is 27 kW in the cooling period. The energy loss is 957 kW and the exergy loss is 127 kW in the heating period. The energy efficiency and the exergy efficiency during the heating period was calculated to be 75% and 41.7%, respectively.