Is 24 volts present
,
measured across PS1
(
orange to yellow)?
See Note #1
Note #1
24 volts = Open Switch
0 volts = Closed Switch
DEFINITION
An error has occurred with the PS1, indica!ng that the pressure
switch is closed when it should be open.
In most cases, the pressure switch is not the problem.
NOTE: Verify pressure switch wiring and tube
rou!ng are correct.
3.1 Fault Code
Cycle power to the furnace
and call for 1 stage heat.
NO
Replace pressure
switch
Verify wiring. If
correct, replace IFC
YES
st
Note #1
24 volts = Open Switch
0 volts = Closed Switch
DEFINITION
An error has occurred with the PS1 indica!ng that the pressure
switch is either open when it should be closed.
In most cases, the pressure switch is not the problem.
NOTE: Verify pressure switch wiring and tube rou!ng
are correct.
PS1 Open errors can occasionally occur when wind
gusts occur. The IFC will a"empt to close both PS1
and PS2 and operate on 2 stage during such an
event.
Note #2
Measured pressure is
nega!ve, greater than refers
to magnitude only.
3.2 Fault Code
nd
YES
YES
Is pressure greater
than pressure switch
label?
See Note #2
Replace pressure switch.
Check opera!on.
Is the inducer
motor running?
Is 24 volts present,
measured across PS1
(orange to yellow)?
See Note #1
NO
Cycle power to the furnace
and call for 1
st
stage heat.
NO
Possible Causes
PS hose, flue piping for obstruc!on
and/or confirm vent size is correct
NO
Is ~120VAC measured
from RD to WH on the
inducer motor within
60 seconds of the W1
call?
Replace inducer
assembly
YES
Verify no voltage at IFC at
IND-LO - IND-N
Replace IFC
NO
Does the igniter
glow within 60
seconds?
PS1 is closed
Yes
YES
NO
Pressure Switch is
okay.
NO
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