Greenheck IG / IGX (464104 IOM) (Pre-2009) - Manual (Page 70)

70
8:1 Staged Furnace Will Not Light
Troubleshooting
24 VAC across 20 and X?
Supply starter relay (ST1) defective or not wired
Replace or wire supply starter relay
No
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
Wire, close or replace heat switch
No
Yes
24 VAC across R and X?
Main disconnect (DS1) open or defective
Close, repaIr or replace main disconnect
Fusing (FU6 and/or FU8) blown
Replace blown fusing
Main transformer (TR1) defective
Replace main transformer
No
Yes
High limit switch (HLC#) open?
Discharge temperature above high limit setting
Let cool then reset high limit (HLC#)
Yes
No
DTI 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 air sensor (TS6)
Yes
No
Blank screen on furnace
controller?
Furnace controller (FX) defective or not powered
Replace or wire furnace controller (FX)
Yes
No
With the combustion blower
(CM#) off, is the N.O. airflow
switch (PSH#) closed?
Continues on next page...
Airflow switch (PSH#) defective
Replace defective airflow switch (PSH#)
Yes
No
Troubleshooting