Day & Night

Requests operating mode, setpoint and supported features through local, wired, wireless or optional thermostat interfaces.

• Remote, timer or local command problem
• Room sensing or thermostat-interface setup
• Wi-Fi or app connectivity problem

Carries the documented power and communication paths between indoor units, outdoor controls and optional distribution equipment.

• Miswired, damaged or unsuitable interconnect
• One communicating unit has lost power
• Board, address or network configuration fault

Converts the supply into the controlled motor power used by variable-speed compressors. Input supply, DC link, output module and cooling are distinct diagnostic stages.

• Missing input or DC-link supply
• Inverter output module or IPM protection
• Heat-sink or electronics cooling problem

Provides room, coil, piping, outdoor-air and discharge-temperature inputs used for demand, protection and refrigerant control.

• Open, shorted or disconnected sensor circuit
• Drifting or incorrect replacement sensor
• Poor sensor contact or location

Meters refrigerant under controller commands, often responding to several measured temperatures and operating states.

• EEV coil, harness or drive fault
• Sticking or restricted valve
• Incorrect inputs or initialization

Moves air across indoor and outdoor coils using model-specific motor drives, feedback and air-direction controls.

• DC motor, drive or feedback fault
• Dirty wheel, coil or blade obstruction
• Louver drive or air-distribution problem

Routes indoor cooling condensate through gravity drains or approved lift pumps and prevents condensation outside the intended pan.

• Blocked or misrouted gravity drain
• Condensate pump or overflow-control fault
• Insulation gap or damaged pan

Connects a matched split-system refrigerant circuit through approved piping or dedicated precharged connections.

• Flare or connection leak
• Kinked pipe or piping outside limits
• Service valve position or charge error

Coordinates several indoor units sharing outdoor capacity, piping circuits and the permitted mode logic.

• Crossed piping or circuit assignment
• Conflicting zone modes or priority
• Incompatible combination or load-sharing problem

Manages frost removal and cold-weather heating through coordinated sensing, compressor control, fans and refrigerant routing.

• Sensor or defrost-control fault
• Outdoor drain or ice obstruction
• Normal defrost, fan delay or capacity limit