Panasonic CS-E18SD3UAW service manual - Page 86

15.5.15 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 35.6°F) 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 When abnormality indication starts again Check the air passage Is there any short circuit? YES For safety reason and to prevent component breakdown, always switch Caution off the power before remove and connect the component. Provide sufficient air passage Check the indoor unit air filter Is the air filter dirty? NO Check the dust accumulation on the indoor unit heat exchanger Is the indoor unit heat exchanger dirty? NO Check if 2/3 way valve is closed? NO Check if indoor fan motor operates normally? YES Check for gas leakage. Is Oil oozing out from the 2/3 way valve? YES YES YES NO YES Check if expansion valve or strainer clogged (ice formed)? NO Check the indoor pipe temperature sensor Does it conform to the sensor characteristic chart? YES NO YES Clean the air filter Clean the indoor unit heat exchanger Open the 2/3 way valve. Replace the indoor unit fan motor and/or indoor unit PCB. Repair the pipe flare or union nuts Reclaim and recharge refrigerant Reclaim and recharge with correct amount of refrigerant. Replace the indoor pipe temperature sensor Replace the indoor unit PCB 86