Heating or conditioning installation of a motor vehicle passenger compartment

The climate control system includes a loop, from the engine cooling system (4), carrying heat and a heat pump loop, containing a cooling fluid; and which contains a compressor (18), and evaporator (16), forming the cold source and a condenser (20), in the engine cooling loop and which forms the heat source. The climate control loop contains a condenser (36) and an evaporator (40) and has an upstream end, with a flow control valve (48), which is downstream of the compressor in the heat pump loop, and a downstream end, which is upstream of the compressor.