McQuay M5MSX 020 A, Manual, Page: 60 / 67

58
Troubleshooting Progress
If the air conditioner is not operating normally, One should follow the troubleshooting steps as stated in the flow chart below .
Check Point (1) – Power Supply
Step-by-step troubleshooting guide for power supply checking.
Check Point (2) – Bridge Diode
Step-by-step troubleshooting guide for identifying bridge diode error.
Red LED
ON?
Check Point (1)
Check Power Supply
Check Power
Supply using
Multi-meter
Voltage
220-240V?
Check Power Line
or Connection Wire
Check Fuse
Is Fuse
Blown?
Nothing Wrong with
Power Supply
Change Fuse
No /
Blinking
Yes
No
Yes
No
Notice the RED LED
and YELLOW LED
Open up the Outdoor
Unit’s Top Panel or
Service Panel
Keep the Main Power
Supply ON
Count the number of blinks indicated by the LED, then
refer to the table shown in page 1-15 and troubleshoot
accordingly
Note:
DO NOT TOUCH ANY OF THE WIRES OR
CONNECTIONS IN THE CONTROL BOX
Check Point (2)
Check Bridge Diode
No
Yes
DC Voltage
~300Vdc
Check DC Voltage across
Bridge Diode or
Electrolytic Capacitor
Fault on PCB
Transformer
Change
Main Board
Any
Conductivity?
Unplug all
Connectors on
Bridge Diode
Check
Conductivity
between all
Terminals
Nothing Wrong with
Bridge Diode
Change
Bridge
Diode
No
Yes
Check AC Voltage
across Bridge
Diode
Voltage
220-240V
Yes
Check Connectors
between IPM &
Main Board
No
Yes
Yes