Hitachi RAC-18WPE Service Manual page 32

4. Reversing valve (4-way valve) control circuit
・
This model is equipped with a reversing valve
(4-way Valve).
・
The reversing valve (4-way Valve) "slides" the
valve in the specified direction for each
operating mode and switches the route of
refrigerant and holds the route with a built-in
permanent magnet.
・
According to an operation command from the
indoor unit microcomputer, the reversing
valve (4-way Valve) control circuit applies current to
the reversing valve (4-way Valve) coil in the
specified direction, for each operating mode and
slides the valve.
・
Just before the compressor starts operation,
the current is applied twice at the interval of 1
sec as shown in Fig. 4-1.
・
During forced cooling operation, just after the
forced cooling switch turns on, the current is
applied twice at the interval of 1 sec as shown
in Fig. 4-1.
・
When the operation stops, the position of the
valve before the stop is held.
・
Before checking the application of current to the reversing valve (4-way Valve), disconnect the connector (CN2) and measure
the resistance of both ends of the connector, to see if it is [2500Ω±10%]. Only when the resistance is normal, check the
application of current using the following procedures.
If the resistance is abnormal, it is caused by either; breakage of a lead wire, or failure of the reversing valve (4-way Valve).
・
The voltage, when measured by a tester during the application of current to the reversing valve (4-way Valve)
(when the voltage is measured)
※Switches the indoor unit to the "Ion Mist operation and air cleaning operation", and keep pressing the "Test switch" of the
outdoor unit electrical part from 1 sec to below 5 sec (while the self-diagnosis lamp LED301 is on).
Afterwards, when the "Test switch" is released, the application of current starts after 1 sec elapses. (Forced cooling operation)
Operating mode
Tester and CN2 terminal
connection point
Analog tester
Digital tester
・
At the voltage measurement timing, when the voltage is measured with a tester, if the tester indicates the values as shown in
the table above, the circuit is functioning normally. (Each tester indicates values differently. Since it is often difficult to read
the values of a digital tester, it is recommended to measure voltage with an analog tester.)
※Since the current is applied only twice in 1 sec, if the timing is missed, correct operations cannot be measured.
※If the main body of the reversing valve (4-way Valve) is functioning normally, it clicks twice synchronously with the voltage
measurement timing.
If this sound is heard, the reversing valve (4-way Valve) is functioning normally.
※If the checking of the application of current becomes abnormal, it is a failure of an electrical part.
Forced cooling
switch (Test switch)
Reversing valve
(4-way Valve)
Compressor
Reversing valve
(4-way Valve)
CN2
12V
Cooling operation
(including forced cooling operation)
⊕ terminal of tester to CN2 pin ④
⊖ terminal of tester to CN2 pin ①
The tester indicates about 80 VDC and returns
to 0 V, and indicates about 80 VDC again.
The tester indicates a large value for an instant and
returns to 0 V, and indicates a large value again.
※In each operating mode, if the tester is reverse-connected to the CN2 terminal,
the tester indicates a value on the – (negative) side.
32
※Voltage measurement timing
1s 1s 1s
ON
OFF
Start
Stop
Fig. 4-1
4
R442
3
2
R441
1
Cooling/Heating
switching relay
(RL4)
12V
HIC
28
29
Fig. 4-2
(Reference) Heating operation
⊕ terminal of tester to CN2 pin ①
⊖ terminal of tester to CN2 pin ④
The tester indicates about 160 VDC and returns
to 0 V, and indicates about 160 VDC again.
The tester indicates a large value for an instant and
returns to 0 V, and indicates a large value again.
AC230V
DB2
Reversing valve
(4-way Valve) relay
(RL3)
Microcomputer
Reversing valve
28
(4-way Valve) on
27 Reversing valve
(4-way Valve) cooling/
heating switching
Cooling Lo
Heating Hi