Sinclair SDV 6 Service Manual page 68

8.1.7 A74 - The error of the AHU Kit slave unit is sent to the master unit
Note: When multiple AHU Kits are connected in parallel, the master AHU Kit (referred to as the master) communicates with the
ODU, and the slave AHU Kit (referred to as the slave) communicates with the master unit. When the slave fails, the slave unit sends
a fault signal to the master unit, and the master unit displays 'A74' (the slave fault).
Error display
Error impact
Error trigger
Error recovery
Possible cause
Troubleshooting
Digital display
Master unit and slave unit: stop. Other IDUs of the same system: operate normally.
ODU of the same system: operate normally.
The error of the slave unit is sent to the master unit
Automatic recovery
 The slave unit is faulty.
 The master unit's main control board is damaged.
Check the running status of
the slave unit, confirm and
resolve the error (1)
in slave unit
After troubleshooting, is the
master unit error code
Yes
Fault cleared
Note:
1. The error code can be queried after the slave is connected to the display box (during field
service, the display box can be temporarily removed from the master unit and connected to the
slave unit)
A74
Error
No
cleared?
Display position (master)
Display box and wired controller
Replace the the main control
board of the master IDU
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