Panasonic CS-Z25UD3EAW Service Manual page 112

18.4.18 H99 (Indoor Freeze Prevention Protection: Cooling or Soft Dry)
Error Code will not display (no Timer LED blinking) but store in EEPROM
Malfunction Decision Conditions

Freeze prevention control takes place (when indoor pipe temperature is lower than 2°C)
Malfunction Caused

Air short circuit at indoor unit

Clogged indoor unit air filter

Dust accumulation on the indoor unit heat exchanger

2/3 way valve closed

Faulty indoor unit fan motor

Refrigerant shortage (refrigerant leakage)

Clogged expansion valve or strainer

Faulty indoor pipe temperature sensor

Faulty indoor unit PCB
Troubleshooting
112