Furnace High Pressure Switch Stuck Open

On a few furnaces i have found the ventor motor seams to be running fine and power is good but fails on pressure switch.

Furnace high pressure switch stuck open.

Replaced circuit board white rodgers 50a50 241 inducer motor comes on then get 3 fl read more. If the switch is open the inducer starts and the resulting pressure change closes the switch. If the inducer comes on the pressure switch is stuck closed. Furnace pressure switch troubleshooting.

This is not a repair. Tapping lightly on the pressure switch body may open the switch and the unit may start. Check for obstructions in the hose. The pressure switch must be replaced.

Using a cloth and a wire brush remove any blockages and dirt from the secondary exchanger and the inducer. The pressure switch works with a small plunger that pushes in and out. 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.

Pressure switch stuck open replaced pressure switch still getting 3 flashes wich means pressure switch stuck open. If you have 24 volts the pressure switch is open and not proving the ventor motor. The source of pressure switch problems can sometimes be a pain to track down. Only oem pressure switches should be used.

After all this the furnace should fire right back up. Take off the end so you can blow through it to the pressure switch. Spray silicon lubricant on the plunger and work it back and forth to loosen the part. If the switch does not close after approx 1 minute the ifc goes into lockout mode.

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. When you do this you should hear a clicking noise. Turn off the power. This might free the switch from sticking.

If there is no disconnect. It doesn t take much pressure so don t blow too hard. 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. Inspect the pressure switch hose.