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