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4:1 Modulating Furnace Will Not Light
Troubleshooting
Ignition controller (IC#)
red LED blinks
7 times or is on
Ignition controller(s) (IC#) failed
Replace faulty ignition controller(s)
High limit switch (HLC#) open?
Discharge temperature was above high limit setting
Let cool, then reset high limit.
Yes
Yes
No
Ignition controller (IC#)
red LED blinks 6 times
Pressure switch (PS2) failure
Repair or replace pressure switch (PS2)
Combustion blower (CM) not functioning
Replace fusing (FU7), combustion blower or relay (CM)
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 4:1 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
...continued from previous page
Secondary transformer (TR6) defective
Replace secondary transformer (TR6)
Amplifier (AMP) defective
Replace amplifier (AMP)
Furnace controller (SC1) defective
Replace furnace controller (SC1)
No
24 VAC between terminals
1 and 2 on the Amplifier (AMP)
No
Yes
24 VDC between terminals
3 and 4 on the Amplifier (AMP)
No
Yes
10 VDC between terminals
5 and 6 on the Amplifier (AMP)
Everything is working properly,
consult factory.
No
Yes
®
Model IG / IGX Make-Up Air