Low-voltage motors are increasingly used in steering, cooling, pumping, and cabin-control subsystems of newenergy vehicles, and excessive temperature can impair their reliability. This paper develops a compact Modelica thermal-network model for an external-rotor low-voltage permanent-magnet synchronous motor. The model represents the principal heat sources, lumped heat capacities, and conductive, convective, and radiative heat-transfer paths. For the tested mass-produced motor, an end-to-end simulation of 30 min of physical operation completed in approximately 2s. Comparison with measured housing temperature for one operating case yielded a maximum relative discrepancy of 5.9%, occurring at the housing-temperature measurement point. These results indicate that the model is a computationally efficient reduced-order tool for the motor and operating range studied. Because the experimental comparison is limited to one motor type and one measured temperature location, accuracy and parameter transferability must be reassessed before the model is applied to other motor topologies or cooling arrangements.