Three-dimensional flow and temperature distributions in a passenger compartment are very important for evaluating passenger comfort and improving A/C system design. In the present study, the Reynolds-averaged Navier-Stokes equations and the energy transport equation were solved, by both quasi-steady and full transient approaches, to simulate a passenger compartment cooling process. By comparing the predictions with experimental results for a simplified GM-10 passenger compartment, the accuracy of the simulation was assessed. Throughout the 800-second period, good agreement was observed between the measured breath-level air temperatures and the prediction of the transient simulation. The quasi-steady simulation underpredicted air temperatures at the very early stage of the cooling process. However, after 200 seconds of cool down, the quasi-steady simulation predicted air temperatures equally as well as the full transient simulation. The current approaches have demonstrated their applicability and accuracy to passenger compartment cooling simulation.Beyond the current application, this simulation methodology may also be used for passenger compartment heating analyses, providing critical parameters and guidelines for passenger comfort assessment and evaluating of the effectiveness of the HVAC system designs.