Abstract: A speed control device for an electric motor fed by a direct voltage source, the device comprising a controlled switch by which the motor voltage is alternately switched on and off under the control of a modulated switching pulse sequence. The switching frequency is higher than the frequency corresponding to the time constant of the electric motor. The switched motor voltage is regulated to a voltage set value corresponding to a desired motor speed by influencing the modulated switching pulse sequence.

Abstract: A vehicle heater with a burner, a fan for the combustion air to be fed to the burner, a heat exchanger for heating the engines's cooling water, which is circulated in a closed circuit, and with a control device. A basic housing is provided substantially in the form of one of a parallelepiped and a semicylinder with an essentially flat, continuous upper housing surface. The basic housing is axially divided into a first housing end section, which is located at a first end and accommodates the burner and the heat exchanger, a middle housing part containing the fan, as well as a second housing end section comprising the control device. The inlet and outlet connections of the heat exchanger as well as a connecting branch for fuel to be fed to the burner are located within the upper surface of the basic housing.

Abstract: A diagnostic system for sensing and displaying malfunctions of a heating apparatus installed in a vehicle, wherein the display is effected by a display device of an on-board timer for the heating apparatus.

Abstract: Flame monitoring is normally performed in a space heater for a motor vehicle in order to stop the fuel supply within a certain period of time in the case of interruption of the flame. If interruption of the flame is detected by measuring the temperature on the heat exchanger or the combustion chamber of the heater in order to detect a possibly relatively rapid temperature drop, it must be ensured that the temperature at the test point can indeed decrease rapidly enough. It is therefore necessary constantly to monitor the electric motor of the blower for the combustion air or for the heating air flowing past the heat exchanger, so that the combustion chamber or the heat exchanger will indeed cool after interruption of the flame. The operation of the blower motor is monitored by briefly interrupting the power supply and measuring the generator voltage generated by the motor that continues to rotate. If there is no generator voltage or it is too low, a malfunction indication is generated.

Abstract: By temperature gradient detection it is determined for the liquid combustion chamber auxiliary heater for motor vehicles, whether e.g. a flame blow-off has taken place, which has to be interpreted as a malfunction and hwich necessitates the discontinuation of fuel supply. Alternatively, it might merely show the switching from a high setting to a low setting. In the latter case a temperature drop to a lower operation temperature occurs also. However, the temperature drop is not as steep as in the case of a flame blow-off. At certain points in time t.sub.1 the target temperature for a point in time t.sub.2 is calculated by the detected temperature according to a certain algorithm having specific device properties as parameters. At this point in time the calculated target temperature is checked for errors.