Heated Air Intake System.

Principles of Gasoline And Disesel Fuel Systems
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(6) Heated Air Intake System. Most later model vehicles are fitted

with a heated air intake system to provide the best performance in all

temperatures with leaner fuel mixtures. The heated air intake system uses a

damper door in the air filter snorkel to select either cold fresh air intake

or heated air that is ducted from a heat stove on the exhaust manifold. The

damper door is moved by a diaphragm that operates by manifold vacuum. The

position of the damper door is determined by a temperature sensor. The

system will keep the temperature of the intake air at about 100 to 115 F.

Operation is as follows:

(a) When inlet air temperature is below 100, the temperature

sensor will allow full vacuum to flow to the operating diaphragm, pulling

the damper door to the heated air position.

(b) When the inlet air is over 115, the temperature sensor will

bleed manifold vacuum off into the atmosphere. This will cause the

diaphragm spring to push the damper door into the unheated fresh air

position.