Battery Contactor Closing Circuit; Ground Service Receptacle - Cessna T182 Series Service Manual

MODEL 182 & T182 SERIES SERVICE MANUAL
side of the battery contactor to the battery box. The
NOTE
contactor will now be free for removal.
6.
To replace the contactor. reverse this proce-
Maintenance of the electronic installation
dure.
cannot be performed when using external
b.
BEGINNING WITH 18266524 AND F18200145.
power.
Application of external power
1. Remove baggage wall.
opens the relay supplying voltage to the
2.
Disconnect ground strap from negative termi-
electronic bus.
For lengthy ground test-
nal of the battery.
ing of electronic systems, connect a well
3.
Cut sta-straps and remove cover from con-
regulated and filtered power supply directly
tactor.
to the battery side of the battery contactor.
4.
Remove nut and washers securing, positive
Adjust the supply for 14-volts and close the
cable. diode assembly and wire to fuse.
Tag wires master switch.
for reinstallation.
5.
Remove nut and washers securing, wire to
NOTE
starter contactor. wire to ground service and wire
to diode.
Tag wires for reinstallation.
When using ground power to start the air-
6.
Remove bolts and washers securing contac-
craft. close the master switch before re-
tor to bracket and remove contactor.
moving the ground power plug. This will
7.
To install contactor reverse this procedure,
ensure closure of the battery contactor
using new sta-straps on cover.
and excitation of the alternator field.
16-29. BATTERY CONTACTOR CLOSING CIRCUIT.
16-30.
DESCRIPTION.
This circuit consists of a
Failure to observe polarity when connecting
5-amp fuse. a resistor and a diode mounted on a
an external power source directly to the bat-
bracket on the side of the battery box. This serves
tery or directly to the battery side of the bat-
to shunt a small charge around the battery contactor
tery contactor, will damage the diodes in the
so that ground power may be used to close the con-
alternator and other semiconductor devices
tactor.
in the aircraft.
16-31.
GROUND SERVICE RECEPTACLE.
16-32. DESCRIPTION.
A ground service receptacle
External power receptacle must be functionally
is offered as optional equipment to permit use of ex-
checked after wiring, or after replacement of
ternal power for cold weather starting or when per-
components of the external power or split bus
forming lengthy electrical maintenance.
A reverse
systems.
Incorrect wiring or malfunctioned
polarity protection system is utilized whereby ground
components can cause immediate engagement
power must pass through an external power contactor
of starter when ground service plug is inserted.
to be connected to the bus. A silicon junction diode
Also refer to Cessna Single-Engine Service
is connected in series with the coil on the external
Letter, SE77-1 (Supplement #1) Dated May 2,
power contactor so that if the ground power source is 1977.
inadvertently connected with a reverse polarity, the
external power contactor will not close. This feature
protects the diodes in the alternator, and other semi-
conductor devices, used in the aircraft from possible
reverse polarity damage.
16-16