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（5）E4 -Indoor Unit motor error of wall mounted air conditioner（PG motor）
Cause: PG motor is equipped with speed feedback signal line. When
the feedback signal of speed is not received by the Indoor Unit main
PCB, it has no way to recognize the rotating speed of motor, which
will be indicated as “Indoor Unit motor error”. Main causes for the
disappearance of speed feedback signal are as follows:
The fan is stucked; 2. The speed feedback component in the motor is
broken; 3. Error of receiving circuit for the speed feedback signal from
the Indoor Unit main PCB.
Inspection path：Is PG motor stucked→Speed feedback line→Speed
feedback terminal connector→Indoor Unit main PCB.
Tools required
for inspection
Multimeter, A PG motor in normal working condition
Frequent
problematic part
Mechanical jam problem of Indoor Unit motor, PG motor, Indoor Unit
main PCB
Inspection
procedure and
key points
1. Check whether the motor can work for a period of time before the
error occurs. If yes, the reason of mechanical jam can be exclude.
2. Disconnect the power supply and move the fan blade of Indoor Unit
machine by hand to see if there’s any resistance. Some occasional
Indoor Unit motor error may relate to bearing coordination.
3. Reconnect the drive wire and speed feedback wire, thus to exclude
any motor error due to connector loosening.
4. Check whether the plug-in terminal of speed feedback on the PCB is
loose, and pull the terminal slightly for inspection if necessary.
5. Replace the motor in the faulted air conditioner with other PG motor
(do not fix it with the fan for the time being), if the main PCB still
indicates “Indoor Unit motor error”, then replace the Indoor Unit main
PCB; if the error disappears, replace the Indoor Unit motor.
The Indoor Unit main PCB will not indicates “Indoor Unit motor
error” when the Indoor Unit motor is still rotating; sometimes such
error will not be reported when obvious motor problems exist (such as
the low-speed rotation due to damaged motor capacitors, or
non-uniform rotating speed due to abnormal speed feedback.
Therefore, patience of the maintenance staff is required for the
troubleshooting of motor error. You shall compare it with the normal
condition, and detect and solve the problem in a flexible way.
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