Midea MCA3U-18HRFNX-QRD0W Service Manual page 38

B For ALARM terminal port CN33
1. Provide the terminal port to connect ALARM ,but no voltage of the terminal port , the power from
the ALARM system (not from the unit )
2. Although design voltage can support higher voltage ,but we strongly ask you connect the power
less than 24V, current less than 0.5A
3. When the unit occurs the problem , the relay would be closed , then ALARM works
 Wiring Diagrams 