Cause 1: M1/M2 cable short-
circuits or cuts off (1)
Properly connect the
cable
Cause 2: The repeater UP and
DOWN ports are not
connected to the
corresponding indoor unit (2)
Properly connect the
cable
Cause 3: The power supply of
repeater is cut off
Check the power supply
of the repeater and
restore the power
supply
Cause 4: Communication
cables of the repeater, ODU,
and IDU have formed a closed
loop (3)
Properly connect the
cable
Cause 5: M1 and M2 of IDU
have been connected to a
matching resistor (4)
Remove the matching
resistor
Cause 6: MDV-Link is not
enabled for ODU (5)
Read the ODU
Installation Manual and
enable MDV-Link
Cause 7: Different
communication networks
(M1M2, PQE, X1X2) are
connected
Connect the
communication cable to
the right port based on
the type of the
communication network
Cause 8: The IDU main control
board or ODU main control
board is damaged
Replace the damaged
main control board
C21 (6)
If the indoor and outdoor units
communicate via MDV-Link
(M1M2)
Note:
1. If you measure the resistance between terminal blocks M1 and M2 of the IDU main control board,
normally this resistance is greater than 1 MΩ.
2. Figure 1 shows the schematic diagram of MDV-Link communication line connection. The connection of
repeater wires must comply with the following requirements. Otherwise, an IDU communication fault may
occur.
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