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