Heated Air Intake System.

Principles of Gasoline And Diesel 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.