Vaillant V 12-025 HWI Training Manual page 24

7 Service Diagnosis
E8
E5 error diagnosis and solution:
Check if high/low pressure valve is open.
Check if the indoor coil temperature sensor
runs normal.
Check if the indoor coil temperature sensor is
not fixed well.
Check if system pressure is normal.
24
Lack of refrigerant
Y
E
S
N
O
Y
E
S
NO
NO
NO
NO
Open the valve.
Replace the sensor.
Re-fix it well.
Re-charge refrigerant.
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