YES
YES
Is pressure measured
greater than
pressure switch
label?
See Note #2
Replace pressure switch.
Check opera!on.
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 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 rou!ng and verify
flue piping has no obstruc!on
NO
Is ~120VAC
measured from BK
to WH on the
inducer motor?
Replace IFCNO
YES
Replace Inducer
Assembly
PS2 is closed & pressure
switch is okay.
Cycle power to the furnace and call for 2 stage heat.
1 stage sequence must be func!onal before 2 stage can
become ac!ve. Insure the inter-stage delay is not in
process when W1 - W2 signals are applied simultaneously
st
nd
nd
YES
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