Is 24 volts present,
measured across PS2?
(brown to yellow)?
See Note #1
Note #1
24 volts = Open Switch
0 volts = Closed Switch
DEFINITION
An error has occurred with the PS2, 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.
3.3 Fault Code
Cycle power OFF, then ON to
the furnace
NO
Replace pressure
switch
Verify wiringYES
Is PS2 oriented
correctly for the
applica!on?
NO
Correct orienta!on
See in this document
YES
YES
YES
Is pressure
greater than
pressure switch
label?
See Note #2
Replace pressure switch.
Check opera!on.
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 PS2 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.
Note #2
Measured pressure is
nega!ve, greater than refers
to magnitude only.
3.4 Fault Code
NO
Check PS hose, flue piping for
obstruc!on and/or confirm vent
size is correct
NO
Is the inducer
motor running?
Replace IFC
NO
Pressure
switch is okay.
Cycle power to the furnace
and call for 2 stage heat.
nd
NO
Is ~120VAC
measured from BK
to WH on the
inducer motor?
NO
YES
Replace Inducer
Assembly
Does the igniter
glow within 60
seconds?
YES
PS1 is closed
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