Toshiba HFC R407C Service Manual page 56

Diagnostic procedure for check code
Check code
[A7]
Suction temperature (TS) alarm (>40°C)
Are the gas pipe and liquid pipe
service valves of the outdoor unit
fully open ?
Yes
Is there a blockage in the
expansion valve on the liquid line?
No
Are the characteristics of TS
pressure switch normal?
(N/C type)
Yes
Insufficient refrigerant, blockage,
pipe breakage.
Check code
[AA]
High pressure sensor (Pd) short circuit
If there is an abnormal output voltage of Pd sensor: Check connector circuit (Pd sensor: PJ7) and output
voltage of the sensor.
If the sensor is normal, replace the outdoor interface PC board.
Sensor characteristics:
Input 12 V DC (± 10%) across red and black leads of the pressure sensor.
Output 0.5 to 4.5 V at 0 to 2.45 MPa across white and black leads of the pressure sensor.
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Troubleshooting
No
Yes
No
Operation cause
1. Outdoor unit service valve closed.
2. Blockage PMV assembly on the liquid line.
3. TS pressure switch error.
4. Insufficient refrigerant, blockage in pipe.
Replace TS pressure switch.
Operation cause
Pd sensor output voltage alarm
Open valves fully.
Replace expansion valve.