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Check SiUS121827E
236 Part 6 Service Diagnosis
8.5 Electronic Expansion Valve Check
Check No.12 Conduct the followings to check the electronic expansion valve (EV).
1. Check if the EV connector is correctly inserted in the PCB. Match the EV unit number and the
connector number.
2. Turn the power off and on again, and check if all the EVs generate latching sound.
3. If any of the EVs does not generate latching sound in the above step 2, disconnect that
connector and check the continuity using a multimeter.
Check the continuity between the pins 5 - 1, 5 - 2, 5 - 3, 5 - 4. If there is no continuity between
the pins, the EV coil is faulty.
4. If no EV generates a latching sound in the above step 2, the outdoor unit PCB is faulty.
5. If the continuity is confirmed in the above step 3, mount a good coil (which generated latching
sound) in the EV unit that did not generate a latching sound, and check if that EV generates a
latching sound.
∗ If a latching sound is generated, the outdoor unit PCB is faulty.
∗ If a latching sound is not generated, the EV unit is faulty.
If the system keeps operating with a defective electronic expansion valve, the following problem
may occur.
Valve
opening
position
Possible problem Check method
Open
Cooling:
Flowing noise of refrigerant in the
unit which is not in operation
Water leakage at the unit which is
not in operation
Operation half due to anti-icing
function
Reset power supply and conduct cooling operation unit
by unit.
Heating:
Flowing noise of refrigerant in the
unit which is not in operation
The unit does not heat the room.
Close
Cooling:
The problem unit does not cool
the room.
Only the problem unit is in
operation, the unit starts pump
down.
(The low pressure of the unit
becomes vacuum.)
Abnormal discharge pipe
temperature
Reset power supply and conduct cooling operation unit
by unit.
Heating:
Refrigerant shortage due to
stagnation of liquid refrigerant inside
the faulty indoor unit
The unit does not heat the room.
Abnormal discharge pipe
temperature
Check the liquid pipe temperature
of no-operation unit.
YES
(R16019)
NO
The EV is not
defective.
Replace the EV
of the room.
Almost the same
as the outdoor
temperature?
Check the low pressure.
(R16020)
YES
NO
Replace the EV
of the room.
The EV is not
defective.
Does the pressure
become into vacuum
zone?
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