Reversible thermal management device for a motor vehicle, said thermal management device having a refrigerant fluid circuit in which a refrigerant fluid circulates, and comprising: - a main loop which comprises successively a compressor, an internal condenser, a first expansion device and an external evaporator/condenser, - a first bypass branch connecting a first connection point arranged on the main loop upstream of the first expansion device, between said first expansion device and the internal condenser, to a second connection point arranged on the main loop upstream of the external evaporator/condenser, between said external evaporator/condenser and the first expansion device, - a second bypass branch connecting a third connection point arranged on the main loop downstream of the external evaporator/condenser, between said external evaporator/condenser and the compressor, to a fourth connection point arranged on the main loop upstream of the first expansion device, between said first expansion device and the first connection point, in which the reversible thermal management device comprises: - a third bypass branch connecting a fifth connection point arranged on the main loop downstream of the first expansion device, between said first expansion device and the second connection point, to a sixth connection point arranged on the main loop upstream of the compressor, between said compressor and the third connection point, said third bypass branch comprising at least one heat exchanger, - a device for redirecting the refrigerant fluid coming from the internal condenser towards the first expansion device or towards the first bypass branch, - a stop valve for the refrigerant fluid, arranged on the main loop between the third and the sixth connection points, - a first check valve arranged on the second bypass branch so as to block the refrigerant fluid coming from the internal condenser, - a second check valve arranged on the main loop between the second and the fifth connection points, so as to block the refrigerant fluid coming from the evaporator/condenser, - a device for redirecting the refrigerant fluid coming from the first expansion device towards the at least one heat exchanger of the third bypass branch or towards the evaporator/condenser. - a main loop which comprises successively a compressor, an internal condenser, a first expansion device and an external evaporator/condenser, - a first bypass branch connecting a first connection point arranged on the main loop upstream of the first expansion device, between said first expansion device and the internal condenser, to a second connection point arranged on the main loop upstream of the external evaporator/condenser, between said external evaporator/condenser and the first expansion device, - a second bypass branch connecting a third connection point arranged on the main loop downstream of the external evaporator/condenser, between said external evaporator/condenser and the compressor, to a fourth connection point arranged on the main loop upstream of the first expansion device, between said first expansion device and the first connection point, - a third bypass branch connecting a fifth connection point arranged on the main loop downstream of the first expansion device, between said first expansion device and the second connection point, to a sixth connection point arranged on the main loop upstream of the compressor, between said compressor and the third connection point, said third bypass branch comprising at least one heat exchanger, - a device for redirecting the refrigerant fluid coming from the internal condenser towards the first expansion device or towards the first bypass branch, - a stop valve for the refrigerant fluid, arranged on the main loop between the third and the sixth connection points, - a first check valve arranged on the second bypass branch so as to block the refrigerant fluid coming from the internal condenser, - a second check valve arranged on the main loop between the second and the fifth connection points, so as to block the refrigerant fluid coming from the evaporator/condenser, - a device for redirecting the refrigerant fluid coming from the first expansion device towards the at least one heat exchanger of the third bypass branch or towards the evaporator/condenser.