Vent Blower Power Circuit Check; Heater Power Circuit Check; Heater And Components Maintenance And Repairs - Piper Navajo Chieftain PA-31-350 Service Manual

13-22. VENT BLOWER POWER CIRCUIT CHECK.
a. With the HEATER SWITCH in the FAN position, electrical continuity (28 volts nominal) should be
present at the following locations. (Refer to Figure 13-7.)
1. Terminal No. 6 on the heater terminal strip.
2. From terminal No. 6 of the heater terminal strip through the radio noise filter to the
ventilating air motor.
3.
The electrical ground circuit for the ventilating air motor is provided by utilizing the
common ground of terminal No. 5 of the heater terminal strip when the landing gear is down. The
ventilating air motor is inoperative when the landing gear is up.
13-23. HEATER POWER CIRCUIT CHECK.
a. With the HEATER SWITCH in the HEAT position, electrical continuity should be present at the
following locations. (Refer to Figure 13-8.)
NOTE
Power for the ventilating air blower is the same as described in
paragraph 13-22, except that power is now supplied through the
HEAT side of the HEATER SWITCH.
1. Terminal No. 1 of the heater terminal strip, to overheat switch, to combustion air pressure
switch and also through filter to combustion air blower.
2.
From terminal No. I of the heater terminal strip through the combustion air pressure switch
to the radio noise filter and onto the combustion air motor also to terminal No. I of the overheat switch.
3. From terminal No. 3 of the overheat switch through the combustion air pressure switch to
terminal No. 2 of the heater terminal strip.
4.
From terminal No. 2 of the heater terminal strip to the ignition unit; to the heater fuel
pump: and through adjustable duct stat switch to terminal No. 3 of the heater terminal strip.
5. From terminal No. 3 of the heater terminal strip through the cycling switch to the fuel
solenoid valve.
In the event that electrical continuity is not present at one or more of the above-listed points, the
wiring must be traced back to the power source. If components are still inoperative after the wiring
inspection, check the individual inoperative components for continuity and, if necessary, replace them.
13-24. MAINTENANCE AND REPAIRS.
Instructions in this paragraph pertain to maintenance of the basic heater and components while the
heater is installed in the airplane. Instructions for removal of components are included provided the
installation permits accessibility.
NOTE
No special service tools are required for normal periodic
maintenance.
Reissued: 9/23/80
4 17
HEATING AND VENTILATING SYSTEM
4B17
NAVAJO CHIEFTAIN SERVICE MANUAL