Troubleshooting SiUS04-702
124 Service Diagnosis
4.3 Freeze-up Protection Control or High Pressure Control
Remote
Controller
Display
A5
Method of
Malfunction
Detection
High pressure control (heat pump model only)
During heating operations, the temperature detected by the indoor heat exchanger thermistor is
used for the high pressure control (stop, outdoor fan stop, etc.)
Freeze-up protection control (operation halt) is activated during cooling operation according to
the temperature detected by the indoor unit heat exchanger thermistor.
Malfunction
Decision
Conditions
High pressure control
During heating operations, the temperature detected by the indoor heat exchanger thermistor is
above 149°F
Freeze-up protection
When the indoor unit heat exchanger temperature is below 32°F during cooling operation.
Supposed
Causes
Operation halt due to clogged air filter of the indoor unit.
Operation halt due to dust accumulation on the indoor unit heat exchanger.
Operation halt due to short-circuit.
Detection error due to faulty indoor unit heat exchanger thermistor.
Detection error due to faulty indoor unit PCB.
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