Piper Navajo PA-31 Service Manual page 697

PIPER NAVAJO SERVICE MANUAL
As optional equipment, one 50-watt wing inspection light is located in the left engine nacelle aft
of the firewall and is controlled by a switch located in the left side panel. A single circuit
breaker protects all these circuits.
d. Instrument panel lighting is accomplished through the use of lights located in
various positions adjacent to individual instruments in the panel and overhead. For aircraft
with Serial Nos. 31-I to 31-7912124. there are up to three rheostats in this circuit to give better
area control. The main rheostat for the pilot's flight panel (all instruments. placards and dials
necessary for the pilot's flight operation) is located in the left side panel. Another rheostat is
located in the overhead switch panel to the pilot's left, for control of lighting in that area. Still
another rheostat (optional with dual instrumentation) is located on the right side of the
instrument panel for control of lighting for the dual instruments. A single circuit breaker
protects the aforementioned. A fourth rheostat is located in the radio junction box for
controlling the lighting of all radio equipment and is protected by the radio accessories circuit
breaker. On aircraft with Serial Nos. 31-8012001 and up, all four rheostats are located between
the two fuel quantity gauges in the overhead panel. These include the pilot's and co-pilot's
lights dimmer (co-pilot's optional) and the overhead panel lights dimmer. A single circuit
breaker protects these circuits. The Avionics lights dimmer is located here also and is protected
by its own circuit breaker.
e. Three cabin lights, one on each side of the instrument panel and one on the fuel
selector panel are controlled by switches adjacent to the lights. Also. two door ajar indicator
lights are located in the overhead panel (Serial Nos. 31-2 to 31-7812129) or in the annunciator
panel (Serial Nos. 31-7912001 and up) and are controlled by switches located at the latching
mechanisms of the cabin and baggage doors. As optional equipment a "No Smoking" and
"Fasten Your Seat Belt" sign can be installed with their switches located on the right cockpit
separation panel on earlier models or in the overhead panel on later models. An optional
reminder chime may also be installed on later models. These circuits are protected by a single
circuit breaker.
f. Independent of the master switch are dome, entrance and baggage compartment
lights. The divider lights are also on this circuit on later models. This circuit is protected by a
fuse on the master contactor next to the battery. The baggage compartment light is controlled
by a switch located in the frame of the baggage door. The dome and entrance lights are
controlled by two-way switches, with one located just inside the entrance door and one in the
pilot's switch panel placarded "Overhead Lights" The divider lights are controlled by switches
located in the appropriate divider.
g. An annunciator panel is incorporated in aircraft with Serial Nos. 31-7812001 and
up. This panel monitors various functions of the electrical system and contains warning lights
grouped together and extending across the upper center of the instrument panel. A press-to-
test switch, located to the left of the panel, illuminates all warning lights and must be held for at
least 3 seconds in order for all lights to illuminate. A dimmer to the right of the panel controls
intensity of the lights and a circuit breaker located in the left side panel controls power to the
annunciator panel.
The gear. oil temperature, cylinder head temperature and fuel quantity indicators and
their associated sender units are protected by a single circuit breaker. The left and right turn
indicators are each connected directly to the main distribution bus through its own circuit
breakers.
The stall warning indicator consists of a horn and a flashing light. The light is located in
the Instrument panel eyebrow directly in front of the pilot and is connected to the lift detector
switch located in the right wing. On airplanes with a stall warning time delay, the delay unit is
located behind the instrument panel on the window channel. The time delay unit assures a horn
sound when the lift detector switch closes and for four seconds after the detector switch opens.
Revised: 9/23/80
ELECTRICAL SYSTEM
4A19