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STEP
10.
Hook an AC voltmeter across PL2- -4 and NEUTRAL- -L2 on the variable speed furnace
control. Is 115- -vac across PL2- -3 and NEUTRAL- -L2?
11.
Replace the variable speed furnace control.
12.
Do you have 115- -vac across PL11- -6 and PL11- -12?
13.
You have an open wire or bad terminal on either the BLACK or WHITE wire between the
variable speed furnace control and the inducer motor. Repair or replace main wire harness.
14.
Are all pins and wire leads in tact on connectors between variable speed furnace control and
the inducer motor?
15.
Fix problem.
16.
Turn power off and disconnect jumper wire across R and W/W1 thermostat terminals.
17.
Turn power back on.
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)
19.
Turn power off.
20.
Do you have continuity between PL11- -2 and PL1- -11?
21.
Do you have continuity between PL11- -10 and PL1- -9?
22.
You have an open wire or bad terminal on either the BROWN or YELLOW wire between
the variable speed furnace control and the inducer motor. Repair or replace the wire har-
ness.
23.
Reconnect PL11 to the inducer motor and put setup switch SW1- -6 in the OFF position.
24.
Does inducer wheel turn freely?
25.
Replace the inducer motor or the inducer motor assembly.
26.
Does the inducer wheel rub against inducer housing?
27.
Does status code 42 flash within 20 seconds after a call for heat?
28.
Turn power off and disconnect jumper from the R and W/W1 thermostat terminals.
29.
Disconnect collector box tube to pressure switch assembly.
30.
Turn power on and jumper the R and W/W1 thermostat terminals.
31.
Does status code 42 flash within 20 seconds after a call for heat?
32.
Reconnect collector box tube to pressure switch assembly.
33.
Reconnect collector box tube to pressure switch assembly.
34.
Disconnect jumper across R and W/W1 thermostat terminals.
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 COM-
PONENT 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.
Turn power off.
37.
Do you have continuity between PL11- -1 and PL1- -7?
38.
You have an open wire or bad terminal on ORANGE wire between PL11 and PL1.
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 LPS and Com on the variable speed furnace control to know when the low heat
pressure switch LPS makes.
40.
Is the inducer motor rotating in direction shown on inducer housing?
41.
Turn power off and disconnect jumper from the R and W/W1 thermostat terminals.
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.
Turn power on and jumper the R and W/W1 thermostat terminals.
44.
Do you have more than 1.0 in. W.C. pressure drop (0.80 in. W.C. 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.
Replace the pressure switch assembly.
46.
Turn power off.
ACTION
28
YES
NO
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