Filters
Replace air filters regularly, as they can become clogged quickly due to dirt and debris from year-round use.
Refrigerant levels
Check that refrigerant levels are within the manufacturer's range and adjust if necessary. Low levels can prevent the heat pump from heating or cooling properly.
Thermostat
Check that the thermostat is level and all connections are secure. If it has lost calibration, an HVAC technician can recalibrate it.
Outdoor unit
Turn off the power and use a hose to wash away debris from the outdoor coils and around the unit. Avoid using a power washer, as it can damage the fins.
Condensate drain
Check the drain for clogs while the heat pump is in cooling mode. Clogs can lead to water leaks and humidity issues.
Other items
Check for refrigerant leaks, lubricate moving parts, inspect belts, and check electrical connections. You can also clean and repair working parts, and inspect and test safety controls.