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Possible causes:
1.Aged input contactor or poor contact
2.Damaged rectifier bridge or capacitors inside the VFD
3.Abnormal DC bus voltage detection circuit
Troubleshooting steps:
1.Confirm that input voltage remains stable, especially during start or loading
2.Check the input contactor, circuit breaker, and fuse for good contact
3.Measure the output of the rectifier bridge for normal operation
4.If rectifier is normal, check if the DC bus capacitors are aged
5.Test by replacing the control board or voltage detection board

During installation or application, the time setting of the UPS with a color screen display is found to be abnormal. The time resets after a UPS restart, or the historical time display is abnormal.
A: 
1. If the time setting on the display screen fails, please check if a button battery is installed on the back of the display screen; or check if the battery has power and try replacing it.
2. If the historical data or time-related functions in the MTR are abnormal, for RMX UPS units, check the button battery on the monitoring board; for HTX33 units, check the button battery on the monitoring interface board. Check if the button battery is installed or replace it.
3. If replacing the button battery does not solve the above problems, the corresponding monitoring board or monitoring interface board needs to be replaced.

1. After shutting down, check whether the fiber plugs on the fiber optic board are loose, and observe whether the fiber head is bright and functioning properly
2. Unplug the fiber and reconnect it to see if the fault is resolved
3. Replace the fiber optic and remove the internal fiber optic card of the unit or the corresponding fiber optic card on the fiber driver board

1.Check the connection circuits of the emergency switch to the sunroof and the front and rear doors. Verify whether the sunroof and the front and rear doors are connected in series and are connected to the control module.
2.Check whether the signal voltage of the roof window circuit and the front and rear door control circuits on the measurement control module is normal (around 12V).
3.If the signal voltage of the skylight circuit is normal but there is still no response, it indicates that the skylight is locked by screws. Remove the screws and it can be used normally.
4.Connect the access control input in the controller above the sliding door and the GND to the ports of control module 70/71.

The actual output voltage is 380V. This is because the voltage generated by the VFD is a PWM-modulated waveform with high-frequency components. To accurately measure the RMS value, a multimeter equipped with an LPF (low-pass filter) function should be used. Our multimeter shows the same reading as the customer's when LPF is disabled. However, once LPF is enabled, the measured output voltage decreases slightly.

If the MVD input voltage is lower than the line voltage and a Grid undervoltage fault occurs, adjust the transformer tap to the -5% position. If the input voltage is too high causing an overvoltage fault in the MVD, adjust the transformer tap to the +5% position.

1. The power module reported this fault. After pulling out the module, do not plug it back into the cabinet. If you do this, the machine will explode and cause a more serious fault.
2. During the warranty period of this large project, it is recommended to conduct a follow-up every three months to understand and help customers maintain the machine. Because when the customer replaces the battery and closes the switch, the machine reports uneven current, which may be caused by the customer's unfamiliarity with the operation. It is necessary to minimize the mistakes of the customer's operation. The loss will be very large if there is a fault in multiple units.

FAQ for "Rectifier Over Temp" and "Rectifier Fail" Alarms
Applicable Models: HRC3320/25 S L
Q: My UPS from your company displayed a "Rectifier Over Temp" alarm during operation today, followed immediately by a "Rectifier Fail" alarm. What causes these alarms?
A: There are two main causes for "Rectifier Over Temp" and "Rectifier Failure" alarms:
1.The temperature detection probe at the relevant detection position is damaged.
2.The circuit monitoring the temperature detection probe is faulty.
Q: How should I resolve these issues?
A: Based on the equipment model you provided, the specific troubleshooting steps are as follows:
1. Check the temperature detection probes (power off the unit first)
1）Locate the rectifier board and disconnect the temperature detection probe connectors (J13/J14/J15).
2）Measure the resistance of the temperature probes: the normal resistance should be 4.6–5.4 k Ω.
3）If any probe shows abnormally low resistance, replace it first, then restart the UPS to check if the alarms are cleared.
2. Check the signal cables between the temperature probes and the control board
1）If the resistance of the temperature probes is normal, reinstall them.
2）Unplug the J12 connector on the rectifier board, power on the UPS, and check whether the alarms still exist.
①If the faults disappear, the rectifier power board is abnormal.
②If the faults remain, the rectifier control board is abnormal.

FAQ For Troubleshooting The Alarm Of ‘Low Battery Voltage’
Applicable Models: HT(R)X 01-20KVA S L
Q: The UPS displays fault code 65. According to the manual, this fault indicates low battery voltage. How should I troubleshoot the UPS?
A: When the UPS shows fault code 65 (low battery voltage), please follow the troubleshooting steps below:
1.Check the actual total battery voltage. If the total voltage is out of the normal range, measure the voltage of each battery cell and replace any defective cells.
2.Check whether the series cables between batteries and the connection cables from batteries to the internal power board of the UPS are securely connected (no loose connections, obvious burning, etc.). 
If any abnormality is found, power off the unit first, replace the cables, then restart the UPS to check if the fault is cleared.
3.Check whether the parameters displayed on the UPS panel / MTR software are consistent with the actual measured values (battery voltage, battery capacity, etc.). If the actual measured values are normal but the displayed values on the UPS screen or MTR software do not match, the internal battery detection circuit of the UPS may be faulty.
Path to view battery data in MTR:Home page → Battery Data
4.If all three checks above show no abnormality, use the MTR software to verify whether the configured battery parameters match the actual battery specifications in use.
Path to check battery parameter settings in MTR:ServSetting → Battery Setting (Please carefully check and compare all items in this section.)