Midea V4 Plus S Series - H7: Faulty Indoor Unit Quantity

MCAC-VTSM-2015-09 R410A All DC Inverter V4+S Series 60Hz
Troubleshooting 141
4.11 H7: Faulty indoor unit quantity
The error will only display on the master unit, all the ODUs will be on standby. It will display when the quantity
of indoor units decrease above 3 minutes.
Note:
* How to check for IDU transformer
The voltage input of IDU transformer is 220V, the voltage output is AC9V (yellow-yellow) and AC13.5V (brown-brown).
* How to check for 485 communication IC
The normal voltage between “P” and “GND” is DC2.5~2.7V, between “Q” and “GND” is DC2.5~2.7V. If the voltage is out of the
normal range, the 485 communication IC is disabled.
* Indoor units should have unified power supply, which can protect the compressor from liquid hammering caused by dropped
indoor units with unclosed EXV.
H7: Faulty indoor unit quantity
Communication terminals P Q E are
loose
Fasten the communication
terminals
Transformer of IDU is disabled
*
Replace the transformer
IDU are not unified power supply*
Insure all the IDU have unified
power supply
485 communication IC is disabled
*
IDU PCB is disabled
Replace the IDU PCB
Some IDU are assigned the same
address
Some IDU are powered off
Set the IDU addresses differently
Power on all IDU
No
No
No
No
No
No
Yes
Yes
Yes
Yes
Yes
P Q E
terminals