McQuay MWM - Page 67

MCQUAY Service Guide Book Diagnosis
66
Condenser fan motor faulty Replace fan motor.
Main PCB faulty Replace main PCB.
9. Disconnection of
discharge thermistor 1 / 2
Poor sensor connection Connect correctly and operate again.
10. Heat Exchanger 1 / 2
high temperature
Discharge sensor malfunction /
poor sensor connection
Connect sensor correctly / replace
sensor.
Insufficient Air Flow / Air Short
Circuit
Ensure no obstacle around the unit.
Heat Exchanger Dirty Ensure no dirt or dust on filter and coil.
Condenser fan motor faulty Replace new motor
Compressor malfunction Replace new compressor.
EXV or EXV PCB faulty Replace new EXV.
Main PCB faulty Replace main PCB.
11. Indoor HEX 1 / 2
abnormal temperature
Poor coil sensor connection Connect sensor correctly / replace new
sensor.
Compressor malfunction Replace new compressor.
Leaking in piping joint Fix the leak point / Change coil.
EXV or EXV PCB faulty Replace new EXV.
Main PCB faulty Replace main PCB.
12. Indoor fan overload Motor internal over current
protection faulty
Replace indoor fan motor.
Winding resistance out of spec
Fan motor short body
Main PCB faulty Replace main PCB
13. Return air sensor short /
open
Faulty Sensor / Poor sensor
connection
Connect sensor correctly / replace
sensor.
14. Outdoor air sensor
short / open
Faulty Sensor / Poor sensor
connection
Connect sensor correctly / replace
sensor.
15. Comp discharge sensor
1 / 2 short
Faulty Sensor / Poor sensor
connection
Connect sensor correctly / replace
sensor.
16. Comp discharge sensor
1 / 2 open
Faulty Sensor / Poor sensor
connection
Connect sensor correctly / replace
sensor.
17. Outdoor HEX sensor 1 /
2 short
Faulty Sensor / Poor sensor
connection
Connect sensor correctly / replace
sensor.
18. Outdoor HEX sensor 1 /
2 open
Faulty Sensor / Poor sensor
connection
Connect sensor correctly / replace
sensor.
19. Indoor HEX sensor 1 / 2
short
Faulty Sensor / Poor sensor
connection
Connect sensor correctly / replace
sensor.
20. Indoor HEX sensor 1 / 2
open
Faulty Sensor / Poor sensor
connection
Connect sensor correctly / replace
sensor.
There are two LEDs in economizer controller board, which are green LED and red LED. Green LED will
blink when economizer controller board is powered-up. Red LED will blink when error(s) occur. Refer the
table below for error codes and their meaning:-
Note:
All the errors occur in economizer controller board will not affect the normal operation of rooftop unit.