System for delaying the switching on and off of a blower motor

摘要

In order to achieve reliable ignition of the fuel/air mixture in the starting phase, initially only the spark plug is switched on. After it reaches its working temperature, the blower motor and the fuel pump are switched on after a delay. When the heating is switched off, initially only the supply of fuel is interrupted and the blower motor is switched off after a delay in order to permit the combustion chamber and the heat exchanger to be cooled. These switching times are to be implemented with a timer circuit and timer which operate according to the principle of capacitor charging in such a way that the times for the switch-on and switch-off delay and their ratio to one another are freely selectable. According to the invention, the switch-off delay of a timer is substantially lengthened if a resistor is connected parallel to its control voltage input after the switch-on delay time has elapsed. <IMAGE>