Electronic Expansion Valve Check - Daikin 4MXL-T Series Service Manual

Check
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
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
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
If the system keeps operating with a defective electronic expansion valve, the following problem
may occur.
236
connector number.
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.
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.
Valve
opening Possible problem
position
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
Open
Heating:
 Flowing noise of refrigerant in the
unit which is not in operation
 The unit does not heat the room.
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
Close
temperature
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 method
Reset power supply and conduct cooling operation unit
by unit.
Check the liquid pipe temperature
of no-operation unit.
Almost the same
as the outdoor
temperature?
YES
Reset power supply and conduct cooling operation unit
by unit.
Check the low pressure.
Does the pressure
become into vacuum
zone?
YES
SiUS121827E
NO
The EV is not
defective.
Replace the EV
of the room.
(R16019)
NO
The EV is not
defective.
Replace the EV
of the room.
(R16020)
Part 6 Service Diagnosis