A heating medium circulation apparatus promptly detects an overheating abnormality of a heating medium caused by insufficient circulation. The heating medium is pumped by a pump in a predetermined direction in a closed-loop circuit connecting a heater and a heat dissipator. An outgoing temperature and a return temperature of the heating medium flowing out of and into the heater are detected. When a heat dissipation-based operation starts, the pump is activated, and heating is started. Heating is temporarily stopped when the outgoing temperature reaches a heating stop temperature. Heating is resumed when the outgoing temperature falls below a heating resumption temperature. An additional condition that the difference between the outgoing and return temperatures is less than a determination value can be added to the condition for resuming heating. An overheating abnormality is detected when the additional condition remains unsatisfied until a determination time elapses after heating is stopped.

A heating medium circulation apparatus promptly detects an overheating abnormality of a heating medium caused by insufficient circulation. The heating medium is pumped by a pump in a predetermined direction in a closed-loop circuit connecting a heater and a heat dissipator. An outgoing temperature and a return temperature of the heating medium flowing out of and into the heater are detected. When a heat dissipation-based operation starts, the pump is activated, and heating is started. Heating is temporarily stopped when the outgoing temperature reaches a heating stop temperature. Heating is resumed when the outgoing temperature falls below a heating resumption temperature. An additional condition that the difference between the outgoing and return temperatures is less than a determination value can be added to the condition for resuming heating. An overheating abnormality is detected when the additional condition remains unsatisfied until a determination time elapses after heating is stopped.