Hussmann Proto-Aire Installation Manual page 66

NOTE: The current draw required by an analog meter (Volt-Ohm Meters or VOMs)
can permanently damage electronic equipment. Never use a VOM to check computer
components or computer controlled systems. Use a Digital Multimeter (DMM) to measure
voltage, amperage, milliamperes, or ohms. If a range is exceeded the display will show OL
(overload).
Alarm LEDs
One exterior and one interior Alarm LED assist in preliminary troubleshooting.
Alarm Light on Alarm Relay
Control Board
ON
OFF
OFF
ON
Exterior
Light Alarm Light
ON OFF
ON OFF
OFF ON
ON ON
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Protocol™ Installation and
Service Manual
Condition
Okay
Monitoring
Alarm
Switchback
Compressor
Safeties Failed