Mitsubishi Electric PQHY-P72ZLMU-A Service Handbook page 342

[ IX Troubleshooting ]
-5- Troubleshooting Principal Parts of BC Controller
1. Pressure sensor
Troubleshooting flow chart for pressure sensor
START
Check whether the pressure sensor or the
connectors of P1 and P3 are connected,
properly
OK?
NO
Operating at the moment?
YES
On the self-diagnosis monitor, measure
Heat source high-pressure 63HS1
Heat source low-pressure 63LS
BC controller pressure P1 (liquid side)
and P3 (intermediate part)
Check whether the result is
63HS1 P1 P3 63LS
OK?
All the compressors of the heat source units to
which the BC controller is connected are stopped.
10 minutes or longer after
the operation stops?
Check P1 and P3 on the self-diagnosis
LED, and check that the detected
pressure is 0.098MPa [14psi] or less.
OK?
Check that the difference between each
detected pressure is 0.098MPa [14psi] or less.
OK?
Both the board and the pressure sensor are normal.
Check whether the refrigerant pipe and the
transmission line are connected correctly between
the heat source unit and the BC controller.
OK?
HWE15150
Note 1
Repair the fault.
Note 2
Check whether the refrigerant pipe
NO
and the transmission line are
connected correctly between the heat
source unit and the BC controller.
YES
NO
NO
NO
Is Pd P1
YES
Fix the relation between the
NO
refrigerant piping and the
transmission line.
YES
Fix the relation between
NO
OK? the refrigerant piping
and the transmission line.
YES
Check whether the contact of the pressure
sensor connector in trouble is not faulty.
NO
Remove the pressure sensor connector
P3 Ps?
from the board, and check the pressure.
YES
Pressure 0MPa [0psi]
Short-circuit between connecter pins #2 and #3
on the circuit board, and check the pressure.
6MPa [870psi] pressure
or more is displayed.
Replace the pressure sensor, which detects
less than 6MPa [870psi] pressure, with the
pressure sensor, which detects 6MPa [870psi]
or more pressure, check the pressure, and
check whether the detected pressure is
displayed normally.
Replace the pressure sensor.
- 333 -
Note 3
NO
OK?
YES
Note 4
Restore contact failure.
NO
YES
NO
YES
NO
OK?
YES
Replace the board.
GB