1508
(EF)
4-way valve trouble in heating mode
Abnormal points and detection methods Causes and check points
Abnormal if 4-way valve does not operate during heating operation.
Abnormal when any of the following temperature conditions is satised for
3 minutes or more during heating operation
1. TH22j − TH21j
[
-18°F [−10°C]
2. TH23j − TH21j
[
-18°F [−10°C]
3. TH22j
[
37.4°F [3:]
4. TH23j
[
37.4°F [3:]
Note:
For indoor unit, the abnormality is detected if an operating unit satises the
condition.
4-way valve failure
Disconnection or failure of 4-way valve coil
Clogged drain pipe
Disconnection or loose connection of connectors
Malfunction of input circuit on outdoor multi controller
circuit board
Defective outdoor power circuit board
TH21:
Indoor intake temperature thermistor (RT11 or TH1)
TH22:
Indoor liquid pipe temperature thermistor (RT13 or TH2)
TH23:
Branch box gas pipe temperature thermistor (TH-A to E)
●Diagnosis of defectives
Make sure to turn the power OFF before connecting/disconnecting any connectors, or replacing boards.
Diagnosis Remedy
Is the connector for outdoor multi
controller circuit board or 4-way
valve coil disconnected or loose?
Reconnect the connector or connect it
tightly.
Yes
Disconnect the connector for outdoor multi
controller circuit board or 4-way valve coil
to check the resistance.
No
Replace the 4-way valve.
Replace the outdoor multi
controller circuit board.
Is the detected voltage normal?
Is it free from any trace of over-
heating or burning?
Is there a resistance detected?
Check the voltage and appearance of the
outdoor multi controller circuit board.
No
Replace the outdoor power circuit board.
Yes
No
Yes
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