STEP
ACTION
YES
NO
GO TO
17
Turn power back on.
18
18
Check the inducer PWM line. To do this disconnect PL11
from the inducer motor and connect a DC voltmeter across
terminals PL11-2 BROWN (+) and PL11-10 YELLOW (-)
then run COMPONENT TEST by turning setup switch
SW1-6 ON. Does voltage across PL11-2 and PL11-10
change between states as shown below?
- State 1 - OFF (1.0 - 4.0 vdc)
- State 2 - MED (7.0 - 10.0 vdc)
23
19
19
Turn power off.
20
20
Do you have continuity between PL11-2 and PL1-11?
21
22
21
Do you have continuity between PL11-10 and PL1-9?
11
22
22
You have an open wire or bad terminal on either the
BROWN or YELLOW wire between the variable speed fur-
nace control and the inducer motor. Repair or replace the
wire harness.
8
23
Reconnect PL11 to the inducer motor and put setup switch
SW1-6 in the OFF position.
24
24
Does inducer wheel turn freely?
26
25
25
Replace the inducer motor or the inducer motor assembly.
8
26
Does the inducer wheel rub against inducer housing?
15
25
27
Does status code 42 flash within 20 seconds after a call for
heat?
28
39
28
Turn power off and disconnect jumper from the R and
W/W1 thermostat terminals.
29
29
Disconnect collector box tube to pressure switch assembly.
30
30
Turn power on and jumper the R and W/W1 thermostat ter-
minals.
31
31
Does status code 42 flash within 20 seconds after a call for
heat?
32
33
32
Reconnect collector box tube to pressure switch assembly.
34
33
Reconnect collector box tube to pressure switch assembly.
40
34
Disconnect jumper across R and W/W1 thermostat termi-
nals.
35
35
Check the RPM feedback line. To do this, connect a DC
voltmeter across terminals PL11-2 BROWN (+) and PL11-1
ORANGE (-), then put setup switch SW1-6 for COMPO-
NENT TEST in ON position. Does the voltage across the
BROWN and ORANGE wires change between states as
shown below?
- State 1 - OFF (11.5 - 12.5 vdc)
- State 2 - MED (9.5 - 10.5 vdc)
36
25
36
Turn power off.
37
37
Do you have continuity between PL11-1 and PL1-7?
11
38
38
You have an open wire or bad terminal on ORANGE wire
between PL11 and PL1.
15
39
Does fault occur a few seconds after the low heat pressure
switch LPS makes?
Note: Check for 24-vac between the N.O. (Normally Open)
contact on low heat pressure switch LPSand Com on the
variable speed furnace control to know when the low heat
pressure switch LPS makes.
40
52
40
Is the inducer motor rotating in direction shown on inducer
housing?
41
25
41
Turn power off and disconnect jumper from the R and
W/W1 thermostat terminals.
42
42
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.
43
43
Turn power on and jumper the R and W/W1 thermostat ter-
minals.
44
44
Do you have more than 1.0 in. wc pressure drop (0.80 in.
wc on 040 model) across heat exchangers when low heat
pressure switch LPS makes?
Note: Check for 24-vac between the N.O. (Normally Open)
contact on low heat pressure switch LPS and Com on the
variable speed furnace control to know when the low heat
pressure switch LPS makes.
45
46
45
Replace the pressure switch assembly.
8
46
Turn power off.
47
32