Panasonic CS-MZ20UB4EA Service Manual page 87

17.4.19 F11 (4-way Valve Switching Failure)
Malfunction Decision Conditions

When indoor heat exchanger is cold during heating (except deice) or when indoor heat exchanger is hot during
cooling and compressor operating, the 4-way valve is detected as malfunction.
Malfunction Caused

Indoor heat exchanger (pipe) thermistor

4-way valve malfunction
Troubleshooting
* Check gas side pipe – for hot gas flow in cooling mode
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