STEP
ACTION
YES
NO
GO TO
22
Connect 1 side of slope manometer with a tee to collector
box pressure tap. Connect other side with a tee to gas
valve pressure fitting. Refer to pressure check diagram in
Appendix C.
23
23
Turn power on and jumper R and W/W1 thermostat termi-
nals.
24
24
Do you have atleast 0.95 in. wc pressure drop (0.75 in. wc
on 040 model) across heat exchangers when fault occurs?
25
26
25
Replace the pressure switch assembly.
8
26
Is inducer motor rotating in direction indicated on the in-
ducer housing?
28
27
27
Replace inducer motor or inducer motor assembly.
8
28
Turn power off.
29
29
Is inducer wheel okay?
31
30
30
If possible, replace inducer wheel. Otherwise, replace in-
ducer motor assembly.
8
31
Is the inducer wheel properly mounted to the inducer motor
shaft?
32
16
32
Is there any frost build-up on the combustion-air inlet?
33
34
33
The problem is caused by reversed vent and combustion-air
pipes or some other moist air entering combustion-air pipe.
16
34
You have excessive restriction in combustion-air or vent
pipe. Also check for proper vent sizing for installation.
16
35
Continue to observe furnace operation for 20 minutes or
until status code starts flashing.
36
36
Does status code 32 flash?
38
37
37
Does a different status code flash?
7
8
38
Turn power off and disconnect jumper wire across R and
W/W1 thermostat terminals.
39
39
Connect 1 side of slope manometer with a tee to collector
box pressure tap. Connect other side with a tee to gas
valve pressure fitting. Refer to pressure check diagram in
Appendix C.
40
40
Turn power on and jumper R and W/W1 thermostat termi-
nals.
41
41
Monitor slope manometer. Does the pressure reading ap-
pear to be stable when fault occurs?
43
42
42
Check for a sag in vent pipe or partially clogged drain trap
or line. Also check for improperly plumbed drainage tubing
within furnace. Install combustion air disk if not used or add
additional restriction to combustion-air inlet.
8
43
Does the pressure reading slowly drop off before flashing
status code 42?
45
44
44
Replace pressure switch assembly. If problem persists,
check wiring for an intermittent connection in low heat pres-
sure switch LPS circuit.
8
45
Check for partially clogged drain trap or line. If furnace is
installed in the horizontal position make sure the furnace is
pitched forward ¼ inch minimum to ½ inch maximum. If fur-
nace is installed in the upflow or downflow position make
sure the furnace is level or pitched forward within ½ inch.
8
Status Code 33
LIMIT CIRCUIT FAULT - This status code indicates the limit, or flame rollout switch is open or the furnace is operating in high-heat only
mode due to 2 successive low heat limit trips. Blower will run for 4 minutes or until the open switch remakes whichever is longer. If open longer
than 3 minutes, code changes to lockout #13. If open less than 3 minutes status code #33 continues to flash until blower shuts off. Flame rollout
switch requires manual reset.
STEP
ACTION
YES
NO
GO TO
1
Turn power off, remove blower access panel, and discon-
nect R thermostat lead. Note current setting of setup switch
SW1-2 and then set it to the ON position.
2
2
Turn power on and depress door switch. Use a piece of
tape to hold switch closed.
3
3
Does status code 33 flash?
11
4
4
Does a different status code flash?
5
6
24
