This might free the switch from sticking.
Furnace high pressure switch stuck open.
The pressure switch must be replaced.
Inspect the pressure switch hose.
If the inducer comes on the pressure switch is stuck closed.
Turn off the power to the furnace by switching off the disconnect switch located near the furnace.
Spray silicon lubricant on the plunger and work it back and forth to loosen the part.
Which is why i made this video that go.
The plunger may not be pulling in completely and may only bob around when the pressure builds up inside the furnace.
When you do this you should hear a clicking noise.
If the switch does not close after approx 1 minute the ifc goes into lockout mode.
After all this the furnace should fire right back up.
The source of pressure switch problems can sometimes be a pain to track down.
Turn off the power.
Pressure switch stuck open replaced pressure switch still getting 3 flashes wich means pressure switch stuck open.
Pushing in the plunger closes the circuit to activate the blower motor so if the switch is stuck in the open position that means the motor will not run.
If your pressure switch is stuck it is most likely a problem in the running of the furnace.
It doesn t take much pressure so don t blow too hard.
Tapping lightly on the pressure switch body may open the switch and the unit may start.
Take off the end so you can blow through it to the pressure switch.
This is not a repair.
Or you test any voltage between 1 to 23 volts then you have bad contacts and the full power is not getting through causing the furnace to fail.
The pressure switch works with a small plunger that pushes in and out.
If there is no disconnect.
Check for obstructions in the hose.
Only oem pressure switches should be used.
If you have 24 volts the pressure switch is open and not proving the ventor motor.
On a few furnaces i have found the ventor motor seams to be running fine and power is good but fails on pressure switch.
Using a cloth and a wire brush remove any blockages and dirt from the secondary exchanger and the inducer.
Furnace pressure switch troubleshooting.
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