This work is a joint development project between Chrysler and CFD Research Corporation (CFDRC). The objective of this investigation is to perform a 3D computational heat transfer analysis in a vehicle passenger compartment, for better climate control, under external thermal radiation. One of the major tasks is to simulate the transient temperature variation in the passenger compartment after the AC unit is turned on.Two physical models were incorporated in the computations, namely, the radiation model and the conjugate heat transfer methodology. The 3D radiation model was employed to evaluate the solar irradiation through the glazed surfaces, namely, the front windshield, the rear window, and the two side windows. Conjugate heat transfer methodology was employed to compute the heat transfer across the glazed surfaces due to heat conduction and convection. These developed models were then integrated and incorporated into the CFD-ACE code, a multi-domain, 2D and 3D combined general equation solver developed by CFDRC.Comparison shows very reasonable agreement between computational results and experimental data obtained from vehicle hot room cool down tests. This study demonstrates that Computational Fluid Dynamics (CFD) technology can be used as a design and prototyping tool for automotive climate control systems.