Samsung MH18ZC1(C2)-09 Service Manual page 37

Troubleshooting
5-4-8 When the 4 way valve (A,B) is not operating
1) Inspection items
(1) Are the 4 way valve A and B under the operating conditions?
(When the COMP A (4 way valve A ) and COMP B (4 way valve B) are on during the
heating operating)
(2) Is the power voltage normal?
(3) Is the connecting of 4 way valve A (CN 75) and B (CN 76) good?
2) Inspection sequence
Put off the outdoor unit power and put it on again after 5 seconds.
Select the heating operation of A(B) room by the remote controller.
Has 3 minutes passed after selection of A(B) room heating?
Is the 4 way valve A(B) on?
Is the voltage shown across the 4 way valve A(B) connector
(CN 75, CN 76) ?
Is the pin no 47(46) of IC 04 ( MICOM) at high (DC 5V) ?
Is the 4 way valve A (B) under operating conditions?
*4 way valve operating conditions
(1) During the defrost control, put the 4 way valve A(B) off.
(2) During the heating operation put the 4 way valve A(B) on.
(3) The changeover of heating to cooling : put the 4 way valve off immediately (in case of B and
C room).
(4) The changeover of cooling to heating : it is on after 170 seconds delay.
5-14
Y
N
N
N
N
Normal
N
Keep 4 way valve off.
Y
Y
Defect of RY 76 (RY 77) contact and coil →Replace
Y
Defect of IC 06 (IC 07 ) output →Replace
Y
Defect of IC 04(MICOM) - replace the IC 04 or PCB
Normal
the Relay
ass'y
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