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
st
stage heat.
NO
Replace pressure
switch
Verify wiring. If
correct, replace IFC
YES
Is PS1 oriented
correctly for the
applica!on?
Correct orienta!on
See this document
NO
YES
2.3 Fault Code
DEFINITION
1
st
Stage Gas Valve not energized when it should
be 10 !mes within the same call for heat .
24VAC not sensed on MVL 10 !mes
Replace IFC
2.4 Fault Code
DEFINITION
High limit output relay is not closed when it
should be
24VAC not sensed on HLO 10 !mes
Replace IFC
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