1. MCQUAY DIGITAL SCROLL SYSTEM
Troubleshooting

2. SELF DIAGNOSIS
MDS Outdoor Unit

3. SELF DIAGNOSIS MDS Outdoor Unit Compressor Protection
High & low pressure switch / Sensor
Overload protection input from compressor
Monitoring Point (Temperature Sensor)
Compressor Discharge
Compressor Suction
Ambient Temperature
Coil Inlet
Coil
Coil Outlet
Compressor

4. 7 segment display on outdoor PCB
SELF DIAGNOSIS
7 segment display on outdoor PCB

5. 7 Segment Display on outdoor PCB
SELF DIAGNOSIS
7 Segment Display on outdoor PCB
Indicator Code

6. SELF DIAGNOSIS
LED of outdoor PCB
ERROR Code

7. SELF DIAGNOSIS MDS Indoor Unit Temperature Sensor Coil Inlet Coil
Coil Outlet
Return air

8. LCD Indicator of controller
SELF DIAGNOSIS
LCD Indicator of controller
ERROR Code

9. SELF DIAGNOSIS ERROR Code LED Indicator of Receiver
Indication light twinkle related to malfunction code :

10. TROUBLESHOOTING
Frequent Malfunction for Commissioning – Communication Error
Symptom:
For A series Outdoor, the 7 segment display C-
For B series Outdoor, the 7 segment display EC78
For Wired Handset, the LCD panel display FC
For LED Display, the Heat LED will be blinking
Potential Caused A:
The communication chip MAX485 of outdoor unit is damaged (Possibility is low. The Communication is tested before ship out)
Solution: To replace the MAX485 chip
Potential Caused B:
The communication wires A/B get crossed each other or not connected
(Most common caused)
Solution: Check on all wiring. Ensure proper tighten and the polarity is consistent.

11. TROUBLESHOOTING
Frequent Malfunction for Commissioning – Communication Error (cont’)
Potential Caused C:
Shielding wire is connected to ground terminal (not grounded).
(Long wiring and running the communication wire together with power supply wire will cause this to happen)
Solution: Ensure the shielding wire is only grounded at the outdoor unit. Do not run the communication wire with the power supply wire together.
Potential Caused D:
Address of indoor are wrongly set
(Caution, the indoor address must be start at ‘0000’ and follow. Do no jump the number.)
Solution: Make sure the address start from ‘0000, did not skip any address and no repetition.

12. TROUBLESHOOTING
Frequent Malfunction for Commissioning – Specific Indoor Communication Error
Symptom:
For A series Outdoor, the 7 segment display CX (X – Indoor Unit Number)
For B series Outdoor, the 7 segment display ECXX (XX – Indoor Unit Number)
For Wired Handset, the LCD panel display FC
For LED Display, the Heat LED will be blinking
Example:
For A series Outdoor, the 7 segment display C3
(Indoor Unit Number 4 not communicating)
For B series Outdoor, the 7 segment display EC03

13. TROUBLESHOOTING
Frequent Malfunction for Commissioning – Specific Indoor Communication Error (cont’)
Potential Caused A:
Indoor Unit PCB has no power supply.
(Possible the power supply to the indoor had been turned off)
Solution: Check the power supply of the indoor power.
Potential Caused B:
Indoor Unit address error.
(Possible the indoor address is not set or duplication)
Solution: Check the indoor model address.

14. TROUBLESHOOTING
Frequent Malfunction for Commissioning – Specific Indoor Communication Error (cont’)
Potential Caused C:
Indoor Unit PCB malfunction.
(Possibility is low. PCB communication is tested before ship out.)
Solution: Replace with another PCB and check the communication
Potential Caused D:
Wrong quantity of indoor set.
(Possible the quantity of indoor unit set in the outdoor PCB is not tally with the actual indoor quantity)
Solution: Check the quantity of indoor unit setting at the outdoor PCB.

15. TROUBLESHOOTING
If the followings malfunction occurred, please follow the steps below to resolve :

16. Thank You