Carrier 38QUS012D8S Service Manual page 124

2.4.4.4. E1 malfunction
Current loop communication:
Malfunction
conditions
Possible causes
Replace the reactor
Replace the reactor
Electrical Control System
Indoor unit does not receive feedback from outdoor unit for 110
seconds. This occurs 4 times in a row.
● Wiring mistakes
● Faulty indoor or outdoor PCB
Power off, then restart the unit 2 minutes later.
Power off, then restart the unit 2 minutes later.
Does a problem still exist?
Does a problem still exist?
Yes
Measure Vs. Is it a positive
Measure Vs. Is it a positive
fluctuation?
fluctuation?
(Vs is the voltage between S and N of
(Vs is the voltage between S and N of
outdoor unit. Red pan-S, Black pan-N.)
outdoor unit. Red pan-S, Black pan-N.)
Yes
Check the outdoor wiring connection. Has
Check the outdoor wiring connection. Has
the problem been resolved?
the problem been resolved?
Yes
Is the reactor
Is the reactor
No
functioning normally?
functioning normally?
Yes
Replace the outdoor main PCB.
Replace the outdoor main PCB.
Power on. Is the error resolved?
Power on. Is the error resolved?
No
Replace the indoor main PCB
Replace the indoor main PCB
No
Check the indoor wiring connection
Check the indoor wiring connection
Yes
Replace the indoor main PCB.
Replace the indoor main PCB.
Power on. Is the error resolved?
Power on. Is the error resolved?
No
Replace the outdoor main PCB
Replace the outdoor main PCB
Troubleshooting
122