Trane 4TWL9048A1000A - Communication Loss Troubleshooting; Communication Loss Troubleshooting Flowchart

4TWL9048A-SF-1C-EN
33
Communication Loss
No AOC / MOC
(Drive) Lights
MOC / Drive
lights on?
Verify 13.8 VDC
on Pins 1 & 6 in
A0C / MOC
Harness
Yes
Unplug 18-Pin
Harness, LSOV,
and EEV Stepper
from A0C and
recheck. MOC /
Drive lights on?
Yes
A0C/MOC
Harness:
Remove HPCO
Condenser Fan
from MOC and
recheck.
No
No
Yes
13.8 VDC on
Pins 1 & 6 in
A0C / MOC
Harness?
No
Yes
Check Line
incoming
voltage
No
Is Line
voltage
present?
No
DCV > 240 VDC
at DCV test
points?
Yes
No
Remove A0C /
MOC COMM
harness, HPCO,
and Condenser
Fan harness.
Recheck for
voltage.
Yes
DCV > 240 VDC
at DCV test
points?
No Yes
Replace AOC
Troubleshoot
Line Voltage
Replace Drive/
AOC
Replace each harness one by
one and troubleshoot
grounding/shorted circuit
Replace Drive
Replace each harness one by
one and troubleshoot
grounding/shorted circuit
Replace Drive
Replace each harness one by
one and troubleshoot
grounding/shorted circuit