Mitsubishi Electric CITY MULTI PUHY-400YMF-B, Service Handbook, Page: 148 / 204

–145–
4) Treatment of Inverter and Compressor Troubles
If the compressor does not work when error codes 4210, 4240, 4310 or 4340 are detected, determine the point of
malfunction by following the steps in the LED monitor display and countermeasures depending on the check
code displayed , then perform the procedures below.
*1 [Cautions when measuring the voltage and current of the inverter’s power circuit.]
Since the voltage and current on the inverter’s power supply side and its output side do not have a sine waveform, the
measurement values will differ depending on the measuring instrument and the circuit measured.
In particular, as the inverter’s output voltage has a pulse waveform, the output frequency also changes, so differences in
measurement values will be great depending on the measuring instrument.
1 When checking if the inverter’s output voltage is unbalanced or not (relative comparison of the voltages between each
of the lines), if you are testing with a portable tester, be sure to use an analog tester.
Use a tester of a type which can be used to judge if the transistor module or diode module is faulty.
In particular, in cases where the inverter’s output frequency is low, there are cases where the variations in measured
voltage values between the different wires will be great when a portable digital tester is used, when in actuality they are
virtually equal, and there is danger of judging that the inverter is faulty.
2
It is recommended when checking the inverter’s output voltage values (when measuring absolute values), that, if a
measuring device for business frequencies is used, a rectified voltage meter (with a symbol) be used.
Correct measurement values cannot be obtained with an ordinary portable tester. (either analog or digital)
No. Check Item Symptoms Treatment
1
2
3
How many hours was the
power kept on before
operation?
When it is restarted, does the
trouble reappear?
Run the outdoor unit with the
wiring to the compressor
disconnected. At this time,
change SW1-1 on the INV
board to ON.
Note) The terminals of the 3
disconnected wires
should be isolated from
each other.
1 If it was kept on for 12 hours or longer
as specified.
2 It was kept on for less than the
specified period.
1
The compressor stops and the same
error code is displayed.
1 The compressor stops and the same
error code is displayed.
2 If the inverter’s output voltage is
output with good balance, *1.
3 If the balance in the inverter’s output
voltage is not good or if the inverter’s
output voltages are all 0 V (a digital
tester cannot be used) *1.
Go to [2].
Go to [2] after keeping the power on for the
specified time.
Perform the check of wiring shown in the
explanation of each error code.
Check the transistor module is faulty. (Go to
“Individual Parts Failure Judgment Methods.”)
Check the coil resistance and insulation resis-
tance of the compressor, and if it is normal, run it
again, and if the trouble occurs again, replace the
compressor.
[Go to “8) Compressor Replacement Procedure”]
* Insulation resistance : 2 M
Ω
or more
Coil resistance : 0.359 ~ 0.716
Ω
Check the transistor module.
Judge that the transistor module is faulty. (Go to
“Individual Parts Failure Judgment Methods.”)
If the transistor module is normal, replace the INV
board, then perform this item again with SW1-1
ON. If the problem is solved and you connect the
compressor again, turn SW1-1 OFF again. Check
the compressor’s coil resistance and insulation
resistance.