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2:1 Modulating Furnace Will Not Light
Troubleshooting
Ignition controller (IC#)
red LED
blinks 7 times or is on
Ignition controller (IC1) failed
(Replace ignition controller)
24 VAC across A and T?
Discharge air selector (TS3) improperly set or faulty
Adjust setting (see staged start-up) or replace sensor
24 VAC across S and T?
Heat transformer (TR5) fault
Replace heating transformer
Discharge temperature was above high limit control (HLC1)
Wait for high limit to cool and reset.
No
No
Yes
Yes
Yes
24 VAC across W1 and X?
Heat switch (S4) open or not wired
Close or replace heat switch (S4)
No
Yes
24 VAC across R and X?
Main disconnect (DS1) open or defective
Close, repair or replace
Main transformer (TR1) fault
Replace main transformer
No
Yes
Ignition controller (IC#)
red LED
blinks 6 times
Combustion blower (CM) not functioning
Replace combustion blower or relay (CM)
Air proving switch (PS2) defective
Replace air proving switch
Yes
No
Ignition controller (IC#)
red LED blinks
1 time, 2 times or 4 times
Improper manifold pressure
Set high and low manifold pressure (refer to the 2:1 Electronic
Modulation Start-Up section)
Faulty spark rod or spark gap does not equal 1/8 inch
Replace spark rod or adjust gap to
1
⁄8 inch
Yes
No
Everything is working
properly, consult factory.
Yes
24 VAC across C and T?
Optional inlet air sensor contact (TS4 open)
Adjust setting reference Blower Start-Up, Step #6
Heat relay (RH) is not energized
Check for loose connections. Repair or replace heat relay (RH)
No
Yes
®
Model IG / IGX Make-Up Air