Mitsubishi Electric CITY MULTI PUHY-P108 Service Handbook page 329

[ IX Troubleshooting ]
(4) In the case of SV2 (Bypass valve) (applicable to the PURY series only)
This solenoid valve opens when powered (Relay ON).
In the case of heating-only or heating-main, the valve turns on when the low pressure (LPS) becomes 0.25MPa [36psi]
or less 5 minutes after the compressor starts.
To check whether the valve is open or closed, check the change of the SV2 downstream piping temperature while the
valve is being powered. When the valve is open, high-temperature gas will run. Do not touch the pipe when checking the
temperature.
(5) In case of SV3 (Bypass valve) (Only P168-P234 types)
This solenoid valve opens when powered (Relay ON).
The valve is normally powered while No.2 Comp is being stopped. (When the discharge temperature of No.1 Comp ex-
ceeds 110°C [230°F], the valve may be turned off.)
To check whether the valve is open or closed, check the change of the SV3 downstream piping temperature while the
valve is being powered. When the valve is open, high-temperature gas will run. Do not touch the pipe when checking the
temperature.
(6) In case of SV4a - 4d [P72 - P144 models], SV4a - 4d, 5a, 5b [P168 - P234 models] (heat exchanger capacity control)
(applicable to the PURY series only)
1) In the case of cooling-only, one or more valves among SV4a - 4d, 5a, and 5b turn(s) on depending on the condition.
Check the operation by LED display and operation sound of the solenoid valve.
2) In the case of heating only, all of SV4a - 4d, 5a, and 5b turn on. The operation can be checked by LED display and
operation sound of the solenoid valve.
3) In the case of cooling-main or heating-main, one or more valves among SV4a - 4d, 5a, and 5b turn(s) on. Check
the operation by LED display and operation sound of the solenoid valve.
4) Refrigerant flow is as shown in the figure below.In the case of cooling-only or cooling-main mode, high-temperature
(high-pressure) flow is shown, and in the case of heating-only or heating-main mode, low-temperature gas or liquid
flow is shown.Refer to the refrigerant circuit figure.Turn on or off the solenoid valve depending on the indoor unit
capacity or the outdoor temperature.Check the LED monitor.Remove the SV coil, open the lid, and check the plung-
er. Pin-face tools, which are specified in service parts list, are required
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