Alpha Technologies APU Control Module (ACM) - Manual (Page 15)

15 018-340-B0-001 Rev. A
3.0 Indicators, Controls and Connectors, continued
3.1 Indicators
The Major and Minor alarm LEDs (1, 2) are red and refl ect the state of the discrete major and
minor alarms monitored by the ACM. A Major alarm indicates failure of a critical component
or some other situation (pad shear, for example) where the system either has gone off-line,
or system failure and/or shutdown is imminent. Major alarms cause the engine to shutdown
immediately and generally prevent further operation. Most major alarms are latched by the
ACM. A site check by service personnel is required to repair the fault and clear the system. A
Minor alarm indicates a system fault which, though not indicative of imminent system failure
or shutdown, requires service attention as the fault condition could worsen leading to a shut
down the system. A site check by service personnel is recommended. The amber Notify LED
(3) represents status information that is not signifi cant enough to be classifi ed as an alarm.
At present, only two items fi t into this category: AC line status and Engine Service Required.
The Communications LED (4) illuminates for two seconds after each communications session
on the Alpha bus. This is a standard that is used throughout the Alpha bus communications
system. The green System status LED (5) indicates that the microprocessor has power and is
operating normally. This LED fl ashes at a 1 Hz rate with a 50% duty cycle. When the ACM is
in factory test mode, this LED will fl ash at a 0.5 Hz rate.