- Excessive suction pressure.
- Excessive refrigerant charge.
- Defective or leaking reversing valve (heating units).
- Insufficient discharge pressure.
Low refrigerant charge;
- Serpentine of the external unit (heating mode) or coil of the frozen internal unit (cold mode).
- Insufficient air flow in the external unit coil (heating mode) or internal unit coil (cold mode).
- Suction line clogged.
- Clogged or frozen expansion device.
- Poor line contact and defrost sensor (units with heating).
- Condenser air flow too high (in cold mode) in relation to external temperature.
