Furnace Pressure Switch Stuck Open

Replaced circuit board white rodgers 50a50 241 inducer motor comes on then get 3 fl read more.

Furnace pressure switch stuck open.

A pressure switch is designed to sense the negative pressure created by the draft inducer motor during the furnace startup and to shut down the furnace ignition if the air pressure is inadequate. Pressure switch stuck open replaced pressure switch still getting 3 flashes wich means pressure switch stuck open. If the inducer comes on the pressure switch is stuck closed. Also noticed the control board was blinking red.

Came home to no heat. The furnace was loud and caused by the draft inducer. 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. Pressure switch fails closed normally this would indicate a failed pressure switch the furnace will test to make sure the switch is open before starting the ventor motor.

The contacts in the switch are either stuck together or moisture has entered the switched and seized it in the closed position. This is not a repair. The pressure switch on a furnace may fail or get stuck in an open position and there are few simple checks you can complete before testing the switch. The pressure switch works with a small plunger that pushes in and out.

Tapping lightly on the pressure switch body may open the switch and the unit may start.