Trane CXAJ series Installation, Operation And Maintenance Manual page 58

Troubleshooting
The suction pressure is too high
Possible Cause
(1) The cooling load is too high (i.e. the water supply temperature is
high).
(2) The expansion valve excessively supplies liquid (i.e. the
superheating capacity is too low, and the liquid overflows to the
compressor).
(3) The suction valve is broken (i.e. the compressor noise is high).
The exhaust pressure is too low
Possible Cause
(1) The refrigerant is charged insufficiently (i.e. the superheating
capacity is high, the sub-cooling capacity is low, and there are bubbles
in the window).
(2) The exhaust valve of the compressor is broken or leaks air.
(3) The low pressure switch is poor.
(4) Operate below the minimum operating environment temperature.
The exhaust pressure is too high
Possible Cause
(1) The condensing air is too little or too hot, and the air flow is blocked.
(2) There is air or noncondensing gas in the system (i.e. the condenser
is unusually hot).
(3) The refrigerant is charged excessively (the sub-cooling capacity
is high, the superheating capacity is low, and the suction pressure is
high).
(4) The system load is excessively high.
(5) The condensing fan or the fan pressure is poorly controlled (i.e.
certain fan is faulty, and the condenser pressure is too high).
The unit cannot run the heating function (limited to CXAJ)
Possible Cause
(1) The control circuit is wrong or poor.
(2) The four-way valve is faulty.
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Handling Method
See the section E.
Adjust the superheat setting, and inspect
whether the temperature sensor is installed in
the gas pipe.
Replace the compressor.
Handling Method
Find out and repair the leakage point, and
recharge the refrigerant.
Replace the compressor.
Replace the poor control element.
Provide the proper exhaust pressure control
or ambient temperature locking switch.
Handling Method
Clear the coil, and inspect whether the fan
and the motor are normal.
Recharge the refrigerant after the system is
vacuumized.
Recycle the excessive refrigerant.
Reduce the load.
Repair or replace the switch.
Handling Method
Inspect the control circuit.
Replace the four-way valve.