737 MAX Flight Crew Operations Manual
Electrical -
Controls and Indicators
MN-FLT-OH-201
6.10.3
4
Frequency Meter
Indicates frequency of source selected by AC meters selector.
5
AC Voltmeter
Indicates voltage of source selected by AC meters selector.
6
Battery Discharge (BAT DISCHARGE) Light
Illuminated (amber) – with BAT switch ON, excessive battery discharge detected.
7
TR UNIT Light
Illuminated (amber) –
• on the ground – any TR has failed.
• in flight –
•TR1 failed; or
•TR2 and TR3 failed.
8
Electrical (ELEC) Light
Illuminated (amber) – a fault exists in DC power system or standby power system.
Note:
Operates only with airplane on ground.
9
Maintenance Test (MAINT) Switch
Used by maintenance.
10
DC Meters Selector
Selects DC source for DC voltmeter and DC ammeter indications.
TEST – used by maintenance.
11
Battery (BAT) Switch
OFF –
• removes power from battery bus and switched hot battery bus when
operating with normal power sources available
• removes power from battery bus, switched hot battery bus, DC standby
bus, static inverter, and AC standby bus when battery is only power
source.
ON (guarded position) –
• provides power to switched hot battery bus
• energizes relays to provide automatic switching of standby electrical
system to battery power with loss of normal power.
March 1, 2021