A Navier-Stokes based finite difference scheme has been developed to simulate the windshield defrosting process of a passenger car. Since the flow field can be decoupled from the temperature equation as the forced convection mode of heat transfer is dominant, it is obtained by solving the steady Navier-Stokes equations for a sufficiently large domain fitted with a general nonorthogonal grid. The temperature field then is computed by carrying out unsteady coupled heat transfer analysis for the internal convection region, the conduction with phase-change region of the windshield and ice, and external free-convection region. The flow field, temperature distributions, heat flux through the interface, melting front at various instants are presented in the paper. The melting front is compared favorably with that observed experimentally.