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Ignition controller (IC#)
red LED
blinks 7 times or is on
Ignition controller(s) (IC#) failed
Replace faulty ignition controller(s)
Yes
... continued from
previous page.
Does the combustion relay
(R9 or CR) close?
Internal high limit tripped (temperature above set point)
Let temperatures cool
Internal inlet air sensor open
Adjust inlet air sensor setting (refer to 8:1 Staged Start-Up section)
Combustion relay (R9 or CR) defective
Replace defective combustion relay (R9 or CR)
No
Yes
Does the combustion
blower (CM) run?
Combustion blower fuse (FU9) blown
Replace combustion blower fuse (FU9)
Combustion blower (CM) defective
Replace defective combustion blower (CM)
No
Yes
No
Ignition controller (IC#)
red LED blinks
1 time, 2 times or 4 times
No
Cycle power to the unit
and wait 30 seconds
Everything is working properly,
consult factory.
Improper manifold pressure
Set high and low manifold pressure
(refer to 8:1 Staged 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
Does the combustion
blower stop after
30 seconds of operation?
Airflow switch (PS2) defective
Replace defective airflow switch (PS2)
Airflow relay (R9) defective
Replace defective airflow relay (R9)
Yes
No
With the combustion blower
(CM) on for at least
30 seconds, is there
24 VAC across T and A or E?
Furnace controller (SC1) defective
Replace furnace controller (SC1)
No
Yes
8:1 Staged Furnace Will Not Light
Troubleshooting
®
Model IG / IGX Make-Up Air