Vaillant V 12-025 HWI Training Manual page 21

E4 Outdoor unit abnormal
E4 error diagnosis and solution:
Check if the winding resistance and operating
current of the compressor are normal
Y
E
S
Check if the high and low pressure is normal
when the unit is running
Y
E
S
Check if the coil pipe sensor is normal
Y
E
S
Check whether the surface of the
condenser is too dirty
N
O
Check whether the capacitance of the outdoor
motor and the fan is damaged
N
O
If the above items are normal,
the electric control board should be replaced.
Split Type Installation Manual
Replace the compressor
NO
Check unit if it is leakage
NO
and fill the refrigerant again.
NO
Cleaned the condenser
YES
Replace the capacitance or fan
YES
Service Diagnosis 7
Replace pipe sensor
EN 21