Abstract: An apparatus for regulating the coolant circuit for an internal combustion engine is equipped with a radiator and a heating system heat exchanger, a water pump, and a thermostat valve which makes possible two circuits in the warmup phase of the engine or at low engine temperatures, one circuit being provided for cooling the engine via a bypass line, and a second circuit being provided to the heating system heat exchanger via a heating system line. A differential pressure valve, regulated as a function of engine speed, is arranged in the bypass line, the bypass line being blocked, and all of the coolant being passed through the heating system line, in the warmup phase or in the phase with a low engine temperature when the speed of the engine is low; and the differential pressure valve opening and uncovering the bypass line at higher engine speeds, a quantitative distribution of the coolant occurring via the bypass line and the heating system line as a function of the design of the differential pressure valve.

Abstract: 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.