Heating device for motor vehicles

A heating device is provided for motor vehicles with a water-cooled internal combustion engine, which heating device has a heat exchanger which is acted on by the cooling water circuit of the internal combustion engine on the one hand and by an auxiliary heating unit which is independent of the internal combustion engine on the other hand. A thermostatically activated switching element causes the hot water to flow via the heat exchanger below a temperature prescribed by the thermostat, when the auxiliary heating unit is switched on, and to flow additionally via the internal combustion engine above this temperature, and causes the engine cooling water to flow via the heat exchanger when the auxiliary heating unit is switched off. In order to achieve low production costs and a large degree of robustness of the switching element it is equipped with a non-return valve whose blocking direction is directed from an outflow chamber to an inflow chamber. The inflow chamber and outflow chamber are connected to one another via at least one leakage hole. The thermostat is arranged in the inflow chamber and provided with an activation element which opens the non-return valve above a prescribed temperature in the inflow chamber and thus enables the through-flow from the outflow chamber to the inflow chamber.