Piper AZTEC D PA-23-250 Owner's Handbook Manual page 39

SECTION II
THE PIPER AZTEC "D"
the heater air, since this will drive more air through the de-
frosters.
When heat is no longer desired, the three position switch
may be turned to the "OFF" position and the manual fuel valve
closed. When the heater has been operating with the airplane on
the ground, turn the switch to "FAN" for several minutes to
cool the heater. It may then be turned off.
Heat may be supplied to warm the cabin before flight by
turning on the master switch, the left auxiliary fuel pump, and
starting the heater. It should not be used in such a way as to
deplete the battery.
The cabin heater uses gasoline from the left main fuel tank
when the crossfeed is off and from both tanks when the cross-
feed is on.
Located in the heater is an overheat lockout switch which
acts as a safety device to render the heater system inoperative
if a malfunction should occur causing excessively high tempera-
tures. This control is located in the downstream end of the vent
jacket, with the reset button on the heater shroud. It is reached
only through the access panel in the left side of the nose section
to insure that the malfunction causing the overheat condition is
corrected prior to further heater operation.
For fresh air ventilation, an air scoop is mounted on the
dorsal fin which draws air into the cabin through overhead vents
in the ceiling. Each individual vent is adjustable for desired air
flow. Two master control knobs are located in the ceiling just
aft of the windshield. These control the air supply to the right
and left overhead vents. Air is exhausted through an outlet on
the floor of the aft baggage compartment.
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