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
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 happen when wind
gusts occur.
S8X2 Only
The IFC will a"empt to close both PS1 and PS2 and
operate on 2
nd
stage during such an event.
Note #2
Measured pressure is
nega!ve, greater than refers
to magnitude only.
3.2 Fault Code
NO
Cycle power to the furnace
and call for 1
st
stage heat.
NO
Possible Causes
Verify PS hose(s) is connected, and
that flue piping has no obstruc!on.
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
& is good
Yes
YES
NO
PS1 is closed & is
good
**
S8B1 / S8X1 measure BK to WH at
the inducer motor and
IND-H – IND-N at IFC
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