Furnace High Pressure Switch Stuck Open

If there is no disconnect.

Furnace high pressure switch stuck open.

If your pressure switch is stuck it is most likely a problem in the running of the furnace. Inspect the pressure switch hose. This might free the switch from sticking. Take off the end so you can blow through it to the pressure switch.

If the switch is open the inducer starts and the resulting pressure change closes the switch. If you have 24 volts the pressure switch is open and not proving the ventor motor. Only oem pressure switches should be used. If the inducer comes on the pressure switch is stuck closed.

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 pressure switch must be replaced. The pressure switch works with a small plunger that pushes in and out.

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. Which is why i made this video that go. 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. Spray silicon lubricant on the plunger and work it back and forth to loosen the part.

When you do this you should hear a clicking noise. The plunger may not be pulling in completely and may only bob around when the pressure builds up inside the furnace. Pressure switch stuck open replaced pressure switch still getting 3 flashes wich means pressure switch stuck open. Furnace pressure switch troubleshooting.

Using a cloth and a wire brush remove any blockages and dirt from the secondary exchanger and the inducer. The source of pressure switch problems can sometimes be a pain to track down. Turn off the power to the furnace by switching off the disconnect switch located near the furnace. This is not a repair.

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. So go ahead and put the hose back on put the access panel back on the furnace turn up the thermostat to its highest setting. On a few furnaces i have found the ventor motor seams to be running fine and power is good but fails on pressure switch.