Greenheck PVF Installation And Operation Manual page 24

Troubleshooting
4:1 Modulating Furnace Will Not Light
In all cases, verify correct terminals as shown on the unit-specific wiring diagram.
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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 24 VAC terminals
on mod valve
Yes
10 VDC between terminals
(+) and (-) on mod valve
Yes
Ignition controller (IC#)
red LED blinks
1 time, 2 times or 4 times
No
Everything is working properly,
consult factory.
24 Indirect Gas-Fired Heat Modules
Yes
Discharge temperature was above high limit setting
Yes
Yes
Combustion blower (CM) not functioning
Replace fusing (FU7), combustion blower or relay (CM)
No
Secondary transformer (TR6) defective
No
Furnace controller (SC1) defective
Yes
(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
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)
Replace secondary transformer (TR6)
Replace furnace controller (SC1)
Improper manifold pressure
Set high and low manifold pressure
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