Piper Navajo PA-31 Service Manual page 966

PIPER NAVAJO SERVICE MANUAL
1.
If the duct switch fails to control the temperature according to the setting, place the control lever
in High "H" position and notice the control variation. A high reading of 250°F ± 10
°
should be obtained
(reading will vary in different applications).
m. Connect a jumper across the terminals of the duct switch to make it inoperative and observe
action of the cycling switch. The cycling switch should cycle to control the outlet air temperature at
approximately 250°F (nominal). This is a function of ambient temperature and airflow conditions. If
operation is within a range of 190°F to 29(0F, the switch is operating normally. If the switch is out of
range, it can be reset as follows:
1.
Turn the adjusting screw clockwise to decrease temperature and counterclockwise to
increase it.
2. After arriving at the proper adjustment, reseal the adjustment screw with a drop of Glyptol
(General Electric's No. 1202) or equivalent on the shaft and switch body.
n. With duct switch still jumped, place a jumper across the cycling switch terminals to check
operation of the overheat switch. Block the ventilating air-outlet and notice if the overheat switch shuts off
the heater. It should open at between 300°F and 400°F. (This is also a function of ambient temperature
and airflow.) After the switch shuts off, remove ventilating air restriction and push reset button until it
clicks. The heater should light and operate.
o. Shut down the heater and check all components visually to make sure no damage has occurred to
any of them.
p. Remove heater and other components from the test set-up and install it in the airplane, in
accordance with instructions in Paragraph 13-20.
13-53. CABIN EXHAUST SYSTEM.
13-54. ADJUSTMENT OF VENT DOOR.
a. If the vent door below the aft portion of the fuselage is found to be in need of adjustment, it will
be necessary to remove the center floor panel at station 222.25 in the cabin area.
NOTE
The vent door should open two inches. If it opens more or less, it
should be adjusted.
b. Adjustment is accomplished by placing the vent in the open position and loosening the clamps
which hold the cable casing in position over the vent door.
c. With the clamps loosened, position the vent door so it opens the required two inches.
d. Move the cable casing until it touches the end of the swivel fitting on the bellcrank and secure it
in this position by tightening the clamps.
e. Replace the floor panel and any other equipment removed from the airplane.
Reissued: 10/12/79
HEATING AND VENTILATING SYSTEM
5D12