: Most boards in this series feature status LEDs. A steady blink usually indicates "Heartbeat" (normal operation), while specific patterns (e.g., 2 blinks, pause) indicate error codes defined in the unit’s wiring schematic.
: Primarily found in industrial air handlers or chillers. Check your unit’s model nameplate to ensure this board is the correct revision for your specific serial number.
: Disconnect all power sources to the HVAC unit. Large industrial systems may have multiple power feeds; verify with a voltmeter.