Cessna 402C - Page 248

SECTION 7
AIRPLANE & SYSTEMS DESCRIPTIONS
FORWARD CABIN AIR KNOB
Gc~'402C
MODEL
The forward cabin air knob directs warm air to outlets located on the
forward cabin bul khead. These direct outlets allow fast warm-up when the
a irp lane is on the ground. Ai rfl ow through the di rect outl ets is can-
pletely shut off by pushing the knob all the way in. The knob may be set .-.
at any intermediate position to regulate the quantity of air to the pilot's
compartment.
RAM AIR CONTROL KNOB
The ram air knob controls ram airflow to the heater. When the knob is
pulled out~ ram air is supplied to the cabin heater. When the knob is
pushed in~ ram airflow to the heater is shut off and cabin air is recircu- ~
lated to the cabin heater. Intermediate positions of this control will
provide a combination of recirculated and ram air.
AFT CABIN AIR KNOB
The aft cabin air knob controls airflow to the passenger compartment.
When the knob is pulled out, the air flows to the heater plenums and then
into the passengers' compartment. Airflow to the plenums is cOOlpletely ...-...
shutoff by pushing the knob all the way in. The knob may be set in any
intermediate position to regulate the quantity of air to the cabin.
DEFROST KNOB
Windshield defrosting and defogging is controlled by the push-pull
defrost knob. When the knob is pulled out, air flows from the defroster
outlets at the base of the Windshield. When the knob is pushed all the way
in~ airflow to the defroster outlets is shut off. The knob may be set in
any intermediate position to regulate the defroster airflow.
HEATER OVERHEAT WARNING LIGHT
An amber overheat warning light provided in the annunciator panel is
labeled HEATER OVHT, see Figure 7-3. When illuminated, the light indicates
that the heater overheat switch has been actuated and that the temperature
of the air in the heater has exceeded 163°C (325°F). Once the heater
overheat switch has been actuated, the heater turns off and cannot be
restarted until the overheat switch, located in the right forward nose
I
compa rtment, has been reset. Th is swi tch is access i b1e from ins ide the nose
wheel
well. Prior to resetting the switch the heater should be thoroughly
checked
to determine the reason for the malfunction.
HEATER OPERATION FOR HEATING AND DEFROSTING
(1 )
m
(4)
(5 )
m
7-44
Battery Switch - ON.
Cabin Air Knobs - PUllOUT.
Defrost Knob - AS REQUIRED.
Cabin Heat Knob - AS REQUIRED.
Cabin Heat Switch - ON.
Cabin Fan Switch - AS REQUIRED.
Ram Air Knob - AS REQUIRED.
1 November 1979
Revision 2 - 3 Aug 1981