When an air-source heat pump water heater malfunctions, you can investigate the following areas:

Power Supply System:

• Check if the power cord is connected properly and if the plug and socket are intact.
• Check if the power switch and circuit breaker are functioning correctly.
• Inspect the various electrical components inside the water heater unit, such as relays and control boards.

Refrigeration System:

• Check if the compressor starts and runs normally.
• Inspect the piping for leaks or blockages.
• Check if the reversing valve is functioning properly.
• Check for refrigerant leaks or insufficient refrigerant levels.

Temperature Control System:

• Check if the temperature sensor is working properly.
• Check if the thermostat switch and thermostat are set correctly.

Water System:

• Check the water pipes for blockages or leaks.
• Check if the water pump is working properly.
• Check if the valves can open and close normally.

Other Components:

• Check if the fan motor is working properly.
• Check the casing and internal connection components for looseness.