Piper Navajo PA-31 Service Manual page 698

PIPER NAVAJO SERVICE MANUAL
On airplanes with Serial Nos. 31-8012001 and up, a heated lift detector is incorporated with the
deice group. This provides heat for the vane, plate and case to assure proper operation during
icing conditions.
The trim and cowl flap indicator circuit consists of a "clamped" power source (a diode
and resistor arrangement connected to the circuit breaker to clamp the output voltage to the
circuit at 20-volts D.C.), voltmeters for indicators and rheostats located on the appropriate
mechanisms to sense their positions. A synchroscope kit is offered as optional equipment.
Both the sender circuits are protected by the same circuit breaker.
The heater switch located to the right of the control pedestal beneath the flap switch, is
placarded "FAN", "OFF" and "HEAT". In the fan position, only the ventilating blower
functions and in the heat position, all heater systems operate. In flight, the ventilating fan
motor is disabled through the gear safety switch by removing its ground. On models with Serial
Nos. 31-8012001 and up, the heater incorporates a reset in flight feature in case of overheating.
An "OVERTEMP" warning light is also provided in the annunciator panel.
A ground vent fan and beverage unit are incorporated on the aircraft as optional
equipment, the ground vent fan being controlled by a switch in the overhead switch panel. The
circuits are protected by separate circuit breakers.
Various configurations for the cigar lighter have been used on the aircraft, refer to the
electrical schematics for proper serial number identification and wiring.
Each pitot tube is controlled independently by a circuit breaker type switch located in the
pilot's switch panel, on earlier models. On later models, they are controlled by rocker switches
in the overhead switch panel.
Other circuits that operate in conjunction with the surface controls, hydraulic system.
fuel system, etc., are explained in their respective sections.
Reissued: 10/12/79
ELECTRICAL SYSTEM
4A20