Heat system and method for a vehicle air-conditioning

It is indicated for a vehicle, a heat system (2), in particular for a hybrid vehicle, comprising a waste-heat heating operation and an alternative-heating and with a HT-cooling circuit (4) for cooling an internal combustion engine (6) of the vehicle, wherein the HT -Kuhlkreislauf (4) has a cooling circuit (8) and a heating circuit (10) which together via a heating circuit (12) and a heating circuit (14) are hydraulically coupled, being arranged in the cooling circuit (8) of the internal combustion engine (6) and in the heating circuit (10) includes a heating heat exchanger (18) and a heat source (20), indoor space heating. The heating circuit (10) is divided into a heating branch (26), in which the heating heat exchanger (18) is arranged, and in a return branch (28) for returning refrigerant in the heating circuit (10), in the return branch (28) comprises a passive locking device (32) is arranged to automatically shut off the return branch (28) in the waste-heat heating operation. The thermal system (2) is structurally particularly simple due to the special wiring and comes with a reduced number of actively controlled and energized valves made. Furthermore, a method for air conditioning a vehicle having a corresponding heat system (2) is specified.