Abstract: A refrigerant heating and cooling system for a motor vehicle includes an inside coil, an outside coil, expansion valves, a reversing valve, a refrigerant compressor, a chiller and a control device. The compressor, outside coil, an expansion valve and the inside coil define a first circuit for cooling the air within the vehicle. The compressor, inside coil, an expansion valve and the chiller define a second circuit for heating the interior of the vehicle. The chiller is a refrigerant-to-engine coolant heat exchanger. When in the heating mode, the chiller functions as an evaporator, the inside coil functions as a condenser and the engine coolant system is the heat source. The control device varies the flow of the engine coolant through the chiller as a function of the engine coolant temperature in order to maintain a relatively constant set temperature within the vehicle.

Abstract: The specification discloses a vehicle cabin temperature control including a thermostat and a power circuit responsive thereto for selectively applying electrical power to a heating/cooling device. The control further includes a protection circuit coupled to the power circuit for interrupting the power applied to the heating/cooling device when a short-circuit is detected.