Midea M-Thermal Arctic HT R290 Mono fault P1

What it means

The system protects the refrigerant circuit from abnormally high discharge pressure and protects the compressor from transient pressure spikes. When discharge pressure (Pc) rises above 3.5MPa, the unit stops running and displays P1.

Likely causes

1. High-pressure switch plug from the inverter control box is loose or misconnected
2. Faulty high-pressure switch
3. Fan not running normally (fan motor or inverter PCB failure)
4. Refrigerant overcharge
5. Refrigerant charge issue
6. Refrigerant system fault causing pressure spike
7. Refrigerant leak from container or system

Where to start

1. Check if the high-pressure switch plug from the inverter control box is loose or misconnected. If yes, reconnect high-pressure switch securely.
2. Power off and power on again. If P1 error still occurs, use a digital multimeter to measure high-pressure switch with buzzer. If buzzer doesn't sound, replace high-pressure switch. If buzzer sounds, replace inverter control box.
3. Reboot the unit and check 'Unit Status-Operation parameter-P1 comp. pressure' on the User Interface. Confirm P1 comp. pressure >3.5MPa when the P1 error occurred. If yes, replace the high-pressure switch.