Furnace Repairs You Might Need When The Pressure Switch Keeps Your Gas Furnace From Igniting

A number of things can cause your gas furnace to keep from igniting. Sometimes, your furnace won't turn on due to a safety mechanism, such as the pressure switch. This could mean the switch is bad or that another part is malfunctioning and causing the switch to do its job and keep the furnace from igniting. Here's a look at the purpose of a furnace pressure switch and what a furnace repair person might do when the switch is keeping your furnace from working.

The Purpose Of The Pressure Switch 

When your gas furnace turns on, the inducer fan starts before the burners light up. This ensures combustion gases will be vented out through the flue. When the fan starts, it creates negative pressure in a tube connected to the pressure switch. This causes the switch to trigger and turn on the gas valve so the burners can ignite.

If the pressure switch doesn't trigger, the burners won't light and your furnace won't make heat. However, if the switch is acting as a safety feature, that could be a good thing. If carbon monoxide isn't pulled up the flue, it might leak out in your house, so the pressure switch plays an important role in protecting your family.

When To Suspect Problems With The Switch

If the switch itself is bad, it might work intermittently, and that makes the problem even harder to diagnose. Different things can cause problems with the switch, so the furnace repair technician has to troubleshoot the furnace to track down the cause.

Your furnace might display an error code that lets you know what's wrong with the switch. You might tell something is wrong by looking at the switch and the hoses and wires connected to it. A loose hose or a hose with a hole in it could interfere with creating the negative pressure needed to trigger the switch.

The Repairs That Might Be Needed

The furnace repair technician has several things to check when your furnace won't start. They may begin with a visual inspection followed by testing the pressure switch with a multimeter. If the switch is bad, it can be taken out and replaced.

If the switch is in good shape, the repair technician may check the flue for a blockage, since a leaf clog could cause problems with airflow. If you have a high-efficiency furnace, condensation might be to blame too, since a hose runs from the condensing unit to the switch.

Other possible problems could be a bad inducer fan motor that keeps the fan from starting, loose connections, and reduced airflow through the furnace. Anything that interferes with the ability of the furnace to send combustion fumes up the vent safely can cause the pressure switch to keep the furnace from starting. While that can be an annoyance, it's also an important way your gas furnace keeps you safe. Contact a furnace repair service for more information.