PURPOSE: To improve the starting and warming performances of engine by feeding air heated through a hot gas combustion heater through a communication path having an air-flow regulating mechanism to an engine intake tube.

CONSTITUTION: A hot gas combustion heater 2 for compensating the insufficient heat source in cold area will burn a combustion tube 22 while rotating a combustion air intake fan 25 and a warm air intake fan 27 through a double shaft motor 28 then the warm air fed through an intake port 26 is heated through a heat-exchanger 29 and discharged through a warm air path 5 to an airconditioner 3. Here, a path 6 communicating between said path 5 and the intake tube 45 of engine 4 is provided while an air-flow regulating mechanism 7 is provided in the path 6. The air-flow regulating mechanism 7 will control the negative pressure exchange valves 73, 74 on the basis of output from a cooling water temperature sensor 81 to regulate the operating amount of an air pressure servo 72 thus to control the opening of a damper 71.