LG GEN2 Series Installation And Operation Manual page 87

Troubleshooting - 4:1 or High Turndown Modulating Furnace
4:1 or High Turndown Modulating Furnace with Microprocessor Controller Will Not Light In all
cases, verify correct terminals as shown on the unit-specific wiring diagram.
...continued from previous page
Microprocessor Alarm:
'pCOe offline' or 'IG furnace
Offline', red blinking
or no light on pCOe?
No
Microprocessor Alarm:
'Discharge temperature
sensor (U04) failure'?
No
Microprocessor Alarm:
'Outdoor temperature
sensor (U05) failure'?
No
Inlet air temperature above
heating lockout setting?
No
Supply air temperature above
Supply Temp Set Point?
No
Ignition Controller (IC#)
red LED blinks 7 times or is on?
No
Continues on next page...
pCOe not connected to main controller
Yes
Yes
Discharge air sensor (U04) not wired or defective
Wire or replace discharge air sensor (U04)
Outdoor air sensor (U05) not wired or defective
Yes
Wire or replace outdoor temperature sensor (U05)
Yes
Increase heating lockout setting to above inlet air temperature
(Be sure to return this setting to the proper temperature after
Wait for discharge temperature to cool or increase supply temp
setpoint sufficiently above inlet air temperature.
Yes
(Be sure to return this setting to the proper temperature
Faulty ground connection to ignition controller (IC#)
Yes
Incorrect voltage supplied to ignition controller Rewire
transformer or correct main voltage supply to unit (Voltage
pCOe not powered
Power the pCOe
Wire to main controller
pCOe defective
Replace pCOe
testing furnace)
after testing furnace)
Repair or install proper ground
to controller must be 24-29 VAC)
Intermittent Controller Fault
Reset power to unit
Ignition Controller(s) (IC#) failed
Replace faulty ignition controller(s)