Porsche P-80 2005, Manual

Page: 31 / 108

911 Carrera (993) Model System
Climate Control Systems Diagnosis & Repair
Page 2.9
Auxiliary Blower
The auxiliary blower supplies hot air forward through left
and right hot air ducts and ensures that the supply of
heated air is not totally dependent on the engine cooling
fan and engine speed. Either fresh air or pressurized
engine cooling air can be fed to the auxiliary blower. This
is controlled by a switchover flap, solenoid valve and
vacuum servo.
In the basic flap position, the auxiliary blower draws in
engine cooling air. In this position, the solenoid is not
energized and the vacuum servo is not actuated.
Engine cooling air is fed to the auxiliary blower under
these conditions:
• Ambient temperature <14° C (11° F) and the mixing
flaps are allowing max. heat
• Max. heat is requested in cold ambient temperatures
• When no heat is requested in summer operation, the
flap is set to the engine air position to improve the venti-
lation of the engine compartment
• Vehicle speed >120 kph (75 mph)
• Failure of the auxiliary blower second stage
• Failure of the vacuum system
• The vehicle is stationary with ignition OFF
Fresh intake air is fed to the auxiliary blower when the
solenoid is energized and the vacuum servo is actuated
under these conditions:
• Normal heating conditions (other than max. heat or no
heat)
• During the monitoring phase when the fan continues to
run after ignition is OFF
• Max A/C is selected
• Air recirculation is selected
The auxiliary blower is located in the engine compartment.