Close this search box.

Furnace Pressure Switch Stuck Up? Common Causes And Troubleshooting

Note: This post may contain affiliate links. This means that at no cost to you, we may receive a small commission for made purchases.

How often does your furnace stop working? If you’re experiencing problems with your furnace, you might want to check out these common issues and their solutions.

Furnaces are essential appliances in every home. They provide heat and air conditioning throughout the year.

The average lifespan of a furnace is around 15 years, depending on the type of furnace.

Furnaces come in two types: natural gas furnaces and oil furnaces. Both types require regular maintenance to ensure they function properly.

If you suspect your furnace has stopped working, you should contact a professional technician immediately.

Here are some reasons why your furnace may be malfunctioning.

The thermostat isn’t set correctly. Make sure that the temperature setting is correct for your area. Check to see if the thermostat is set too high or low.

You can also adjust it manually by turning the dial clockwise or counterclockwise until it’s at the right setting.

The filter needs cleaning. A dirty filter will cause your system to run inefficiently. Clean the filter once a month to prevent clogs from forming.

The blower motor is not running. This could mean that there is no airflow through the vents. Turn off the power to the unit and turn it back on.

If this doesn’t fix the problem, call an HVAC technician.

There is something blocking the vent pipe. Look for any debris inside the vent pipe. Remove any blockages before calling a professional.

What Exactly Is A Furnace Switch?

A pressure switch is used to detect the pressure of air in a system. When the switch detects pressure, it moves to the closed position.

Once the switch closes, it allows the system to turn on the fan and blower. The fan and blower help to circulate warm air around the house.

To prevent carbon monoxide poisoning, it’s important to turn off the gas valve before attempting any repairs or troubleshooting.

You should also make sure to turn off the gas supply at the main shut-off valve before working on the furnace.

A pressure switch is a safety device used to detect negative pressure inside a furnace. It shuts off the ignition if there isn’t enough oxygen or too much carbon monoxide in the room.

Furnace pressure switches are normally open when the furnace is running and closed when the furnace is turned off.

They measure the airflow through the heat exchanger and turn on the ignition if there’s enough oxygen and carbon monoxide.

Switches protect the system against insufficient airflow (combusted air and flue products). These switches also prevent the condensate drain system from getting clogged.

Possible Troubleshooting Issues

Your furnace doesn’t seem to be working properly. Try cranking on your furnace to see if the problem is resolved.

If you can’t reach the problem, then call an HVAC professional for help.

Malfunctioning Switch

A furnace pressure switch is a safety device that prevents your furnace from operating when the temperature reaches unsafe levels.

When the switch is stuck open, it means that something is wrong with the switch. Fortunately, this problem is an easy fix.

An electrician should be called to check out the switch and then fix it. This job shouldn’t cost much money.

However, if the switch isn’t working correctly, it could cause serious problems.

Your house might become extremely hot or cold. You could also get carbon monoxide poisoning.

Blocked Pressure Switch Hose

A lot of people get their furnace pressure switches stuck open because of a clogged or disconnected hose.

This causes them to run constantly, even though there is nothing wrong with the furnace. An expert should be called instead to fix the problem.

Other Causes

Furnace Pressure Switch Stuck Up? Common Causes And Troubleshooting

There are many possible reasons why your furnace might be having problems. You should check the manual first before calling an expert.

Furnace condensate drains should be cleaned regularly. Clogs can occur if debris builds up in them. 

A stuck open pressure switch means the furnace won’t work properly. Recycle the furnace to fix the problem.

Short the pressure switch wires manually by connecting them with a jumper. If the furnace starts when the wires are connected, then the pressure switch is working.

A blocked drain can cause a backup in the blower fan housings. This can lead to pressure issues, including a pressure switch stuck open.

Furnace fans create negative pressure inside the house, but if there is a blockage in the ducts, the fan won’t be able to create this negative pressure.

As a result, the pressure switch remains in the OPEN position. Fixing this problem requires removing debris from the ducts.

How To Fix The Pressure Switch

Turn off the main power switch first, then work on the pressure switch. Don’t touch any wires when working on a furnace.

Inspect The Switch

The switch is stuck because there is some kind of blockage inside the circuit. You must unblock this blockage before repairing the switch.

You can use a multimeter to check the resistance of the switch, but you should consult a technician first.

Reset The Furnace Control

The IFC unit needs to be reset. High Limit Switch keeps tripping. The furnace high limit switch should be replaced.

Check For A Blockage In The Venting

You should check the chimney first. Then you should remove all the debris in the ducts. Finally, you should test your unit by running it.

There are many reasons why a pressure switch could be stuck open. A blocked exhaust vent is the most common reason.

Other possible causes include Snow, birds’ nests, Leaves, and Soot buildup. Cleaning the exhaust vent should fix this problem. 

A blockage could be caused by something stuck inside the valve or by something blocking the flow of water.

You must try to remove whatever is causing the problem before replacing the pressure switch.

Check The Suction/Hose Tube

Carefully locate where the pressure hoses are connected and use a flashlight. Look closely at it to make sure it’s tight and clean. Replace if necessary.

Pressure switches are used to detect the pressure inside the ducts. A pressure switch is connected to an exhaust vent by a hose.

If the hose is broken, cracked, or disconnected, then the pressure switch stays closed, and the furnace doesn’t turn on. You need to replace the hose if it is cracked or damaged.

You also need to reconnect the hose if it is disconnected. If you have a multi-stage furnace, then you have more than one pressure switch.

Check your furnace hoses for water build-up or damage. Clean them out to make sure that the pressure switches work properly.

The Drain Line

Ensure that there is no blockage or obstruction in the drain line by cleaning out any debris.

Clean out any excess water from the inducer fan housing as well as the drain pan (see also ‘ Is A Drain Pan Required Under A Water Heater? ‘).

Call An Expert

You should call an HVAC technician if you’ve tried everything above and nothing seems to be working.

A specialist will come with special tools to inspect your furnace thoroughly. If he finds anything wrong, he’ll fix it right away.

How Do I Test For Continuity Within The Pressure Switch Terminals?


Pressure switches are used to turn furnaces on or off.

To test continuity across the pressure switch terminals, disconnect the wires from the pressure switch, touch the terminals with your multimeter leads, and use your multimeter on the continuity setting.

If the furnace is turned off, then the pressure switches should be opened.

A furnace should heat up when turned on. You should see the inducer fan spinning. Test the pressure switch by putting a meter in continuity mode.

If the pressure switch passes all the previous tests, then there is nothing else wrong with the pressure switch.

Reattach the wires to the pressure switches and turn on the furnace.

How Do I Test For Voltage In The Terminals?

A furnace pressure switch tests for voltage across its terminals. If there is no voltage, then the furnace pressure switch is closed.

A pressure switch is a mechanical device that measures the air pressure inside your house.

When the air pressure drops below a certain point, the pressure switch opens and allows electricity to flow into the heating element.

When the air pressure rises above a certain point, the switch closes again and cuts off power to the heating element.

How Do I Replace The Pressure Switch?

Replacing the pressure switch on an electric furnace is easy. You’ll need a screwdriver, a wrench, and a flashlight. To replace the pressure switch, you’ll also need a new fuse.

The easiest way to locate the right pressure switch is by using the model number.

Look up your model number on the Internet, and then use Google to search for the pressure switch.

To replace a pressure switch in an air conditioner, follow these steps: turn off power to the air conditioner. Open up the access panel.

Disconnect the two wires coming out of the pressure switch. Disconnect the hose connected to the pressure switch. Make a note of which port is connected to the hose.

Remove the old pressure switches. Most times, you just need a screwdriver to remove the pressure switch from the air conditioner.

Install the new pressure switch inside the air conditioner. The new pressure switch might come along with a bracket that holds the switch in place.

If that’s the case, then you need to attach the new bracket if it is different from the old one.

If it’s the same type of bracket, feel free to reuse the old one. Reconnecting the hose to the new port and reconnecting the wires to the new terminal should work fine.

However, if your old pressure switch had three terminals, then you need to connect them to the common and normally open terminals.

Turn the power back on and go ahead and test the furnace.

Final Thoughts

Pressure switches are simple devices. They do what they say they do. But as with any electronic device, there can be problems.

It’s best to check the pressure switch before turning on the furnace.

If you find that the pressure switch doesn’t pass the test, then you have a problem.

Find out how to fix it and get back to enjoying the warmth!

author avatar
Anthony Barnes
Anthony Barnes is the founder of Water Heater Hub and a second-generation plumber by profession. Before developing Water Heater Hub, Anthony Barnes was a full-time plumber, and he has undertaken a wide variety of projects over the decades. As a second-generation plumber, it was easy for Anthony to get used to the technicalities of all from a tender age


On Key

Related Posts

Is Drano Bad for Pipes? The Truth Revealed

Note: This post may contain affiliate links. This means that at no cost to you, we may receive a small commission for made purchases. When it comes to dealing with clogged drains, many homeowners turn