Bosch IDS BOVB20 Installation Instructions Manual page 36

Installation Instructions
H8 (Pressure transducer (PT) fault)
Is the pressure
transducer (PT) wired
correctly?
Yes
Run
unit in cooling
or heating mode. Is the
suction pressure within 50 PSI
of checkpoint No.9
(cooling) or No.10
(heating)?
Yes
Did the control board fail?
No
Restart system
Figure 63
3 6 |
No Correct wiring
Replace pressure
No
transducer
Replace control board
Yes
WARNING: HAZARDOUS VOLTAGE

When measuring resistance , make sure the unit is powered
off and wait 3 min before taking measurement.
P0 (Control board is over-heated)
Is there poor heat
dissipation?
No
Did the outdoor
fan motor fail?
No
Are T5 and
Tf connections at
control board
correct?
Yes
Is the
resistance of
Tf in the range of
Table 16?
Yes
Did the control
board fail?
No
Restart system
Figure 64
Bosch IDS BOVB20 Split System Heat Pump - BTC 761701316 C (02.2022)
Refer to control board
replacement instructions to
Yes
ensure there is good contact
between the heat sink
and control board
Replace motor
Yes
Correct T5 and Tf
No
connections
Replace Tf sensor
No
Replace control board
Yes