A steady-state mathematical model of a small-capacity Automotive Air Conditioning System (AACS) working with the refrigerants R134a (1,1,1,2-tetrafluoroethane) and R1234yf (2,3,3,3-tetrafluoropropene) is developed. The model considers the major components of the system, namely, the swash plate compressor with fixed stroke, thermostatic expansion valve (TXV) and the compact heat exchangers (flat-tube, louvered-fin evaporator and condenser). In order to verify the mathematical model, an experimental facility has been developed for testing the AACS and experiments are conducted with R134a. The experimental results are also validated with published data. The effects of various operating conditions, namely, the condensing air temperature, condensing air velocity and the compressor speed, on the performance of the AACS are predicted for both R134a and R1234yf. The results of the simulations with R134a and R1234yf are compared with the experimental results obtained with R134a. The results show good agreement with the experimental results, with most of them showing less than 10–15% of variations from the experiment results. The uncertainty analysis is performed and showed that the most of validations follow below 10% difference.