Mitsubishi Electric PQHY-P120THMU-A, Service Handbook

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[
IX
Troubleshooting ]
- 333 - HWE09080 GB
-6- Inverter (YHMU-A)
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Replace only the compressor if only the compressor is found to be defective.
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Replace the defective components if the inverter is found to be defective.
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If both the compressor and the inverter are found to be defective, replace the defective component(s) of both devices.
(1) Inverter-related problems: Troubleshooting and remedies
1) The INV board has a large-capacity electrolytic capacitor, in which residual voltage remains even after the main power is
turned off, posing a risk of electric shock. Turn off the unit, leave it turned off for at least 10 minutes, and check that the voltage
across FT-P and FT-N terminals on the INV board or the terminals at both ends of the electrolytic capacitor is 20V or below
before checking inside the control box.
(It takes about 10 minutes to discharge electricity after the power supply is turn off.)
2) The IPM on the inverter becomes damaged if there are loose screws are connectors. If a problem occurs after replacing some
of the parts, mixed up wiring is often the cause of the problem. Check for proper connection of the wiring, screws, connectors,
and Faston terminals.
3) To avoid damage to the circuit board, do not connect or disconnect the inverter-related connectors with the main power turned
on.
4) Faston terminals have a locking function. Make sure the terminals are securely locked in place after insertion.
5) When the IPM or IGBT is replaced, apply a thin layer of heat radiation grease that is supplied evenly to these parts. Wipe off
any grease that may get on the wiring terminal to avoid terminal contact failure.
6) Faulty wiring to the compressor damages the compressor. Connect the wiring in the correct phase sequence.
Press the tab on the terminals to remove them.
[YHMU-A]