Piper Navajo PA-31 Service Manual page 937

PIPER NAVAJO SERVICE MANUAL
13-38. DUCT SWITCH. (Refer to Figure 13-30, 13-31 or 13-32.) There is a micro switch added to the
duct switch on the heater system No. 2 installations. This switch is wired to the existing terminals on the
face of the duct switch.
a. Removal:
1. Place the control lever arm in high position and loosen the allen-head set screw that secures
the arm to the temperature selector shaft. Slide the lever and arm off the shaft.
2. Disconnect the two electrical leads from the terminals on the exposed face of the switch.
3.
Remove the two wires from the duct switch to the micro switch if installed and mark them
for proper reinstallation.
4. Remove the two attaching screws and washers from the duct.
5. Carefully lift out the switch and gasket (if gasket is used).
b. Cleaning and Inspection:
1.
Brush off any dust or lint from the switch operating mechanism (exposed inside the duct)
and wipe external surfaces with a clean cloth.
c. Installation:
1.
Insert the switch carefully, with gasket (if used), into the ventilating duct opening and
install the two attaching screws and washers.
2. Connect the two electrical leads to their respective terminals, as marked during removal. If a
micro switch is incorporated into the duct switch, connect the two wires from the micro switch to the duct
switch terminals.
3.
Set the temperature selector shaft at the high stop. Then carefully place the control lever
arm on the shaft at the high position and lock the lever by tightening the allen-head set screw. (Do not over
tighten.) Rotate the lever arm to make sure it clears the electrical terminal screws and support bracket when
it is moved to the high position.
4. If a micro switch is incorporated into the duct switch, set the micro switch to activate at the
very last movement of the control lever arm in the high heat position.
5.
Operate the heater with the duct switch set above ambient temperature to check operation.
(Refer to Paragraph 13-52 for additional switch tests and setting instructions.)
13-39. OVERHAUL INSTRUCTIONS. After 500 heater hours or after each heating season (whichever
comes first), the heater should be removed from the airplane, disassembled, all parts thoroughly inspected
and necessary repairs and replacements made prior to reassembly. Detailed step-by-step instructions are
included for a complete heater overhaul. In some instances, however, inspections may reveal that it is
unnecessary to remove certain parts, and, if so, those portions of the overhaul procedures may be
eliminated.
NOTE
For disassembly and reassembly operations, refer to the exploded
view drawings and the parts list.
Reissued: 10/12/79
HEATING AND VENTILATING SYSTEM
5C7