Bosch BOVB 18 Series Installation Instructions Manual page 33

Installation Instructions
P4 (High compressor discharge temperature (T5) protection)
Diagnosis
Check whether the service
valves are open
Yes
Check whether the T5 is normal
according to Table 28 (between
temperature and resistance)
Yes
Check whether outdoor and
indoor unit motor is abnormal
or whether coils (outdoor and
indoor) are blocked
No
Check whether the charge is
correct by subcooling
according to installation guide
in charge mode when cooling
Yes
Check whether the EEV/TXV is
normal for throttle
(wire seated coil)
Yes
Check whether the compres-
sor is normal (abnormal noise,
abnormal vibration)
Yes
Figure 52
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Handling
No
Open the service valve
No
Replace the T5 sensor
Yes Replace the fan or
remove all the barriers
No
Adjust the charge
Re-power and check
No
again, if the same, replace
the EEV.
No
Replace the compressor
Error Code Description
E4 Temperature sensor fault (T3, T4, T5)
H8 Pressure transducer (PT) fault
F1 High pressure switch (HPS) fault
Table 18
E4 (Temperature sensor fault (T3, T4, T5)
Diagnosis
Check whether sensor
T3/T4/T5 are seated
and normal
(T4 for Heat Pump only)
Yes
Unplug the sensor, check
whether the resistance of
T3/T4 is in the range of
Table 24
Yes
Unplug the sensor, Check
whether the resistance of T5
is in the range of Table 28
Yes
Check whether the display the
shows the same error code
when re-powered on
Yes
Figure 53
H8 (Pressure transducer (PT) fault)
Diagnosis
Check whether pressure
transducer (PT) wiring are
seated and normal
Yes
Is the pressure transducer
working properly? Compare
the data between pressure
measurement and No 9
(cooling) or No 10 (heating)
check point value (by pressing
check button)
Yes
Check whether there is the
same fault
Yes
Figure 54
Bosch IDS BOVB 18 | 33
Handling
No
Reseat the sensor
according to wiring diagram
No
Replace the fault T3/T4
sensor
No
Replace the fault T5 sensor
No
Keep running
Handling
No Wire according to the
diagram correctly
No
Replace the pressure
transducer
No
Keep running
Data subject to change