Mitsubishi Electric PUHY-HP120TNU-A, Service Handbook

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[8-8 Troubleshooting LEV Problems ]
28
- chapter 8 HWE18240_GB
8 Troubleshooting Based on Observed Symptoms
8-8-2 Possible Problems and Solutions
The specifications of the outdoor unit (outdoor LEV) and the indoor unit (indoor LEV) differ. Therefore, remedies for each fail-
ure may vary. Check the remedy specified for the appropriate LEV as indicated in the below column.
Malfunction
mode
Judgment method Remedy Target
LEV
Microcomputer
driver circuit fail-
ure Disconnect the control board connector and connect the check
LED as shown in the figure below.
Resistance : 0.25W 1k
ȍ
LED : DC15V 20mA or more
When the main power is turned on, the indoor unit circuit board
outputs pulse signals to the indoor unit LEV for 10 seconds, and
the outdoor unit circuit board outputs pulse signals to the outdoor
unit LEV for 17 seconds.
If any of the LED remains lit or unlit, the drive circuit is faulty.
When the drive circuit has a
problem, replace the control
board. Indoor
Outdoor
LEV mechanism
is locked If the LEV is locked, the drive motor runs idle, and makes a small
clicking sound.
When the valve makes a closing and opening sound, the valve
has a problem. Replace the LEV. Indoor
Outdoor
Disconnected or
short-circuited
LEV motor coil Measure the resistance between coils (red-white, red-orange,
brown-yellow, brown-blue) with a tester. When the resistance is
in the range of 150
ȍ
± 10%, the LEV is normal.
Replace the LEV coils. Indoor
Measure the resistance between coils (red-white, red-orange,
red-yellow, red-blue) with a tester. When the resistance is in the
range of 100
ȍ
± 10%, the LEV is normal.
Replace the LEV coils. Outdoor
(LEV2a,
LEV2b)
Measure the resistance between coils (red - white, red - orange,
brown - yellow, brown - blue) with a tester. When the resistance
is in the range of 46
ȍ
± 3%, the LEV is normal.
Replace the LEV coils. Outdoor
(LEV1,
LEV4,
LEV9)
Incomple sealing
(leak from the
valve) When checking the refrigerant leak from the indoor LEV, run the
target indoor unit in the fan mode, and the other indoor units in
the cooling mode. Then, check the liquid temperature (TH2) with
the self-diagnosis LED. When the unit is running in the fan mode,
the LEV is fully closed, and the temperature detected by the
thermistor is not low. If there is a leak, however, the temperature
will be low. If the temperature is extremely low compared with the
inlet temperature displayed on the remote controller, the LEV is
not properly sealed, however, if there is a little leak, it is not nec-
essary to replace the LEV when there are no effects to other
parts. If there is a large amount of
leakage, replace the LEV. Indoor
Faulty wire con-
nections in the
connector or
faulty contact 1. Check for loose pins on the connector and check the col-
ors of the lead wires visually Check the continuity at the
points where an error occurs. Indoor
Outdoor
2. Disconnect the control board's connector and conduct a
continuity check using a tester.
6
5
4
3
2
1
1 k LED
Thermistor
(liquid piping
temperature detection)
Linear Expansion Valve