Mitsubishi Electric CITY MULTI PUHY-400YMF-B, Service Handbook

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1) Power cord problem
(constant capacity unit is discon-
nected from the power source)
2) Power board fuse (F01, F02) is
blown.
3) Power board is defective
4) Control board is defective
1) Heavy-load operations exceeding the
unit’s capacity.
2) Power source abnormality
a. Power source voltage drop
b. Power source voltage defect
3) Defective power cord
4) Defective compressor
a. Compressor open phase, earth
fault
b. Compressor lock-up
1) There is an open phase in the power
supply (L1, L2, L3, N).
2) The power supply voltage is dis-
torted.
3) A fuse is defective.
4) T01 is defective.
5) The circuit board is defective.
Checking code Meaning, detecting method Cause Checking method & Countermeasure
4106
4108
4115
Power off
abnormality
(Variable
capacity unit)
Over-current
Protection
(Outdoor unit)
Power supply
sync signal
abnormality
(Variable
capacity unit)
1 Cannot operate because the
constant capacity unit is dis-
connected from the power
source.
1 First detection
If the 51C2 is operated during
operation of the No. 2 or No. 3
compressor the outdoor unit
will temporarily stop. After 3
minutes, it will restart.
2 Second detection
After 1 minute since the
above restart, if the 51C2
operates again there will be
an error stop, and “4108” will
be displayed.
3 After the outdoor unit stops
and the No. 2 compressor re-
starts there will be 1 minute
during which the unit is in pre-
liminary error stop mode. The
preliminary error stop display
will blink on the LED.
The frequency cannot be deter-
mined when the power is switched
on.
(The power supply’s frequency
cannot be detected. The outdoor
fan cannot be controlled by phase
control.)
Measure the voltage in each part of
the constant capacity unit
1
Power source terminal block (TB1)
2
Power board (CN20)
3 Control board
• Confirm unit operation conditions
• Voltage check on power source
terminal block TB1
• Open phase check
• 52C2 connector, power cord check
• Power cord check, compressor re-
sistance check. (Mega-check)
• Operate in no-load status.
• Remove the compressor power
cord, check the power cord
insulation and operate.
→
If there is no abnormality
when 52C2 is turned ON, the
compressor is defective.
Check before the breaker, after the
breaker or at the power supply termi-
nal blocks TB1 or TB1A, and if there is
an open phase, correct the connec-
tions.
If the power supply voltage waveform
is distorted from a sine wave, improve
the power supply environment.
If F1 on the MAIN board, or F3 is
melted, (Resistance between both
ends of the fuse is
∞
), replace the
fuses.
To judge failure of the T01, go to “Indi-
vidual Parts Failure Judgment Meth-
ods.”
If none of the items in 1) to 4) is appli-
cable, and if the trouble reappears
even after the power is switched on
again, replace the MAIN board (when
replacing the circuit board, be sure to
connect all the connectors, ground
wires, etc. securely).