Diamond DA 42 NG, Maintenance Manual

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AIRCRAFT
DA 42 NG AMM Electrical Power
Doc # 7.02.15
Rev. 4
24-00-00
Page 11
15 Mar 2018
(13) Avionics Master Relay
The avionics master relay connects the AVIONICS BUS to the RH MAIN BUS. The
AV. MASTER switch controls the avionics master relay.
(14) Elect. Master Switch
The ELECT. MASTER switch is located on the bottom of the instrument panel, left side. It is a
rocker switch that has 3 sets of contacts. When the switch is set to ON the contacts operate as
follows:
)
The coil of the battery relay is connected to ground and the battery relay operates.
)
The ground side of the LH alternator switch is connected to ground.
)
The ground side of the RH alternator switch is connected to ground.
(15) Start Switch
The START switch is operated with a key. The switch can be turned to LH or RH and must be
held against a spring to maintain the selected position. Setting the START switch to LH or RH,
with the ELECT. MASTER switch set to ON and the related ENGINE MASTER switch set to ON
will cause the related engine starter motor to operate.
(16) Engine Master LH / RH
The LH and RH ENGINE MASTER switches are located either side of the START switch. Each
switch is similar and has 4 sets of contacts which operate as follows:
)
The related engine starter control system is energized.
)
The alternator regulator is enabled and the ECU backup battery relays are energized.
)
The LH / RH ECU BUS is connected to the related engine ECU A and ECU B EECU system.
(17) Alternator LH and Alternator RH Switches
Each engine alternator relay has a control switch. The control switches are labeled ALT LH and
ALT RH. When the ELECT. MASTER switch is set to ON setting the ALT LH or ALT RH switch
to ON gives a ground to the related engine alternator relay. The alternator relay operates and
the related alternator output is connected to the related MAIN BUS.