PRINCIPLES GASOLINE/DIESEL FUEL SYSTEMS - OD1620 - LESSON 1/TASK 2
(6) Heated Air Intake System. Most later model vehicles are fitted
with a heated air intake system to provide the best performance in all
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