Greenheck IG / IGX (464104 IOM) (Pre-2009) - Manual (Page 68)

68
24 VAC across terminals
X and A?
Internal high limit switch tripped
Allow discharge temperature to cool
Inlet air sensor contact open
Adjust inlet air sensor setting (refer to 4:1 modulation start-up)
Furnace controller (FX) defective
Replace furnace controller (FX)
24 VAC across 20 and X?
Supply starter relay (ST1) defective or not wired
Replace or wire supply starter relay
No
No
Yes
Yes
Call for heat relay (CH)
closed?
Call for heat relay (CH) defective
Replace call for heat relay (CH).
No
Yes
24 VAC across W1 and X?
Heat switch (S3) open or not wired
Close or replace heat switch
No
Yes
24 VAC across R and X?
Main disconnect (DS1) open or defective
Close, repair or replace
Fusing (FU6 and/or FU8) blown
Replace blown fusing
Main transformer (TR1) fault
Replace main transformer
No
Yes
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4:1 Modulating Furnace Will Not Light
Troubleshooting
DT1 displayed on furnace
controller?
Discharge air sensor (TS2) not wired or defective
Wire or replace discharge air sensor (TS2)
Yes
No
OT1 displayed on furnace
controller?
Outdoor air sensor (TS6) not wired or defective
Wire or replace outdoor temperature sensor (TS6)
Yes
No
Blank screen on furnace
controller?
Furnace controller (FX) defective or not powered
Replace or wire furnace controller (FX)
Yes
No
Troubleshooting