Thermostatic Air Control System: Operation
Air intake of air cleaner is connected to fresh outside air and to pre-heated air through a snorkel connected to a shroud over the exhaust manifold. A vacuum motor controlled flap allows fresh air, pre-heated air, or a combination of both to enter air cleaner housing as needed. An ambient temperature sensitive vacuum switch, located in air cleaner housing, is used to control manifold vacuum to vacuum motor which moves the flap. See Fig 1 .
At ambient temperatures of less than 75°F (24°C), temperature vacuum switch will allow vacuum to reach vacuum motor and air flap will allow pre-heated air to enter air cleaner housing. At ambient temperatures greater than 75°F (24°C), temperature vacuum switch will gradually leak vacuum into air cleaner housing which will cause vacuum motor and air flap to return to its normal position, allowing fresh outside air to enter air cleaner housing. Temperature sensitive vacuum switch will modulate amount of air flap opening, depending on ambient air temperature, to give a blend of fresh and pre-heated air as necessary.