Is 24 volts present,
measured across PS2?
(brown to yellow)?
See Note #1
Note #1
24 volts = Open Switch
0 volts = Closed Switch
3.3 Fault Code
Cycle power OFF, then ON to
the furnace
Is PS2 oriented
correctly for the
applica!on?
NO
YES
Correct orienta!on
See in this document
NO
Replace pressure
switch
Verify wiringYES
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.
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 PS2
(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 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
Cycle power to the furnace
and call for 2nd stage heat.
NO
Check PS hose, flue piping for
obstruc!on and confirm vent size is
correct
NO
Pressure switch
is okay.
Is voltage measured
from
RD- WH
BK-RD
BK-WH
at the inducer motor?
Replace inducer
assembly
NO
Is PS2 oriented
correctly for the
applica!on?
Correct orienta!on
See in this document
NO
YES
YES
Call Technical Support
YES
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