Hitachi RAC-50FPA, Service Manual

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3. Latch-type reversing valve control circuit
・
This model comes equipped with a latch-type
reversing valve.
・
The latch-type reversing valve is so designed
that its valve is "slid" in a specified direction
according to a specific operation mode, thereby
switching freezing channels and retaining the
built-in permanent magnet.
・ The latch-type reversing valve control circuit is
so designed that, in response to an operation
command from the indoor microcomputer, the
reversing valve coil receives a current in a
specified direction according to a specific
operation mode, thereby sliding the valve.
・
The product is energized twice at increments
of 1 second as illustrated in Fig. 3-1, starting
immediately before compressor startup.
・
During forcible cooling, the product is energized
twice at increments of 1 second as illustrated in
Fig. 3-1, starting immediately after the forcible
freezing switch is turned on.
・ When stopped, the product holds the valve in
the position where it was before stoppage.
Fig. 3-1
1
2
3
4
Reversing valve
R４４１
ＤＢ１
Cooling/heating
switchover relay
（ＲＬ１）
Reversing valve relay
（ＲＬ２）
ＣＮ２
ＶＨ−２Ｐ
（
2P lacking
）
ＡＣ220Ｖ-230V
１２Ｖ １２Ｖ
ＨIＣ
IC2
Reversing valve ON
Reversing valve cooling/
heating switchover
Cooling Lo
Heating Hi
Microcomputer
Forcible cooling
switch (test switch)
※ Timing for voltage measurement
1s 1s 1s
Reversing valve
Compressor
ON
OFF
Start
Stop
Red
Cooling/heating relay coil Reversing valve relay coil
Fig. 3-2
・
Before conducting an energization check of the reversing valve, detach the connector CN2, measure the resistance at both
ends of the connector, and ensure that it is within the range [400
Ω ±
100
Ω
]. Check for energization only when the above
test proves the product to be normal. If it is abnormal, it should be a lead wire break or a reversing valve failure.
・
Voltage when measured with a tester while the reversing valve is energized (at the timing for voltage measurement)
※
Hold down the "test switch" of the outdoor electrical parts for at least 1 second.
Energization begins 1 second after the "test switch" is pressed.
Tester type
Analog tester
Connect pin ① of the CN2 to the positive terminal of the tester.
Connect pin
④ of the CN2 of the negative terminal of the tester.
The pointer will swing in reverse direction.
The tester will display a large negative value, go back to 0 V,
and then display a negative large value.
Digital tester
Connect pin ④ of the CN2 to the positive terminal
of the tester.
Connect pin
① of the CN2 to the negative terminal
of the tester.
The pointer will keep swinging up to about 150 V DC,
goes back to 0 V, and then swing back to about 150 V
DC.
The pointer will momentarily display a high value, go
back to 0 V, and then display a large value again.
・ When the voltage is measured with a tester with the timing for voltage measurement, and if the pointer swings as illustrated
in the above table, then the product should be normal. (There are dispersions with testers. Moreover, a digital tester often
results in its reading being illegible. An analog tester is therefore recommended.)
※ The product is energized only twice a second. Missing the timings will therefore result in failure to measure normal operations.
※ If the reversing valve proper is normal, it will synchronize with the timing for voltage measurement and the reversing valve
itself will click twice. If this click is heard, the reversing valve should be functioning normally.
※ If the energization check shows an abnormality, the electrical parts should be out of order.
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