Increasing acceptance of tractor cab air conditioning is evidenced by the rapid population growth of air-conditioned agricultural vehicles. Both field- and factory-installed units made available by numerous manufacturers provide wide variations of system capabilities to meet various customer requirements. The present air conditioning state-of-the-art utilizing the vapor compression system supports manufacture of functional units of adequate capacity to meet most agricultural cab requirements. However, the severe applications to which most off-the-road (including agricultural) vehicles are subjected in comparison with automobiles require some unique design innovations. Further development of system components to provide increased system reliability and durability will result in increasing customer acceptance and satisfaction.