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