Furnace code in 3 pressure switch stuck open should I replace switch

The switches do fail. However, make sure all the orifices are open and not clogged with debris. `Remove the hoses and carefully clean them out with a paper clip.

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Originally Posted by ma0641

The switches do fail. However, make sure all the orifices are open and not clogged with debris. `Remove the hoses and carefully clean them out with a paper clip.

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thanks for the tip. I've done that and I cleaned and checked a number of related parts. It was working for a while ,then would 'nt fire. The vent and blower motors are working , ignitor glows and sometimes fires. The controler then blinks 3times by the chart it means pressure switch stuck open. Do you think the switch is gone or could it be??

I would make sure to clean the flame sensor using fine sandpaper or steel wool. Pressure switches are relatively inexpensive and easy to replace. You can test it by measuring voltage across the terminals when the induced fan is running and calling for heat. Should show 24 volts Dc or AC depending on heater. You can Aldo test jump the terminals and try the heater. If it starts and runs replace the switch.

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Originally Posted by ma0641

I would make sure to clean the flame sensor using fine sandpaper or steel wool. Pressure switches are relatively inexpensive and easy to replace. You can test it by measuring voltage across the terminals when the induced fan is running and calling for heat. Should show 24 volts Dc or AC depending on heater. You can Aldo test jump the terminals and try the heater. If it starts and runs replace the switch.

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O.k I'll try to test and jump.the sensor looked clean but ill take some emery cloth to itand see what happens. Thanks again.

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Originally Posted by sam1962

O.k I'll try to test and jump.the sensor looked clean but ill take some emery cloth to itand see what happens. Thanks again.

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DO NOT use emory cloth. Scotch brite pad or fine steel wool only. Emory & some sandpaper will leave permanent scratches which can & do cause either damage or excessive deposits.