The furnace HVAC pressure switch, aka air switch, is a safety measure device found near the draft inducer motor in your home so that it will stop the combustion process, which could lead to carbon monoxide poisoning from lethal gases. An air pressure switch is crucial since it can prevent fires, and ensure the furnace works when venting air pressure, thus being safe and saving money.
If your display shows a “combustion air switch failed to close” error, your furnace combustion air switch fails for three common reasons. The good news is that failing mechanical pressure switches are easy to fix.
Although using a technician to diagnose why your air switch failed is often the best call, you can do this yourself if your air pressure switch, AKA air switch, fails for something like the air hose detaches. In our guide, you can learn more about what to look for when the combustion air switch failed to close. You’ll know what to check and why the switch failed to close by the end.
Rubber hoses break, and if this is all it is, you are lucky. Either way, your troubleshooting technique can be enough rather than spending a fortune on a technician. (Read Do Snowblowers Have Air Filters)
What Is A Combustion Air Switch?
The airflow switch confirms the combustion fan, which comprises the combustion blower and combustion motor, is functional and generates the minimum air pressure for safe lighting of the burner.
the air pressure switch detects tiny air pressures and the passage of air and water.
The automated safety feature sits near the combustion air pipe and the draft inducer motor.
The safety measure device turns down your furnace if it detects negative pressure from your draft inducer motor while measuring the flow.
What Would Cause A Pressure Switch Not To Close?
The most likely causes for your air switch’s failure to close are: A block or leak in the combustion air pipe, issues with the combustion motor or wheel faulty-dirty, dirty flame sensor, or you could find tubes are pressure kinked, loose, or clogged.
Here are the main three areas on the safety measure device found most often.
Obstructed And Clogged Venting
If the flue pipe is blocked, your furnace fan creates problems when venting out combustion gases. As a result, when the pressure drops, it could cause the air switch to fail and stay open.
If you have a blocked flue pipe, your furnace draft motor will experience problems trying to vent out combustion gases.
As a result, your air switch may fail to close. Damaged flue pipes are not uncommon and are caused by materials such as leaves, ice, and snow, all of which can cause harmful gases to flood your home.
Damaged Or Detached Air Switch Hose
The air switch can quickly identify if the inducer motor is working if the hoses are well connected.
However, if one or more of the rubber hoses break, fracture, or come loose, you’re in for a major headache. As a result, the air switch cannot close since it no longer receives an accurate reading from the hose.
The air switch can instantly identify if the inducer motor works appropriately as long as the hoses are correctly connected.
If one or more of the rubber hoses break, crack, or hole, or become detached, you may have a problem with your air switch.
It cannot close because it no longer receives adequate readings from the hose and remains open. (Read Guide to Cleaning Battery Terminals Without Disconnecting)
Air Switch Malfunction
The third factor that may create problems with your combustion air switch is if it has failed.
An ohmmeter can help here. If you discover the issue is with the switch, you are better fitting a new switch.
However, before attempting to replace a single switch, ensure your heater is turned off. Besides, all the wires linked to the air switch must be disconnected from the switch terminals.
The issue maybe with your air switch. You can use your ohmmeter to check your air switch and replace it if necessary.
How Do You Bypass Combustion Air Switch?
If you have a pressure switch on your furnace, you can see how to bypass a pressure switch through jumping to help diagnose this HVAC issue.
Should I Bypass a Pressure Switch on a Furnace?
A gas furnace pressure switch bypass is a valid test to isolate the issue you are trying to troubleshoot.
This isn’t the answer to your problem, but it will help you figure out if the problem is with the pressure switch or something else.
Clogs or broken hoses coming from the draft inducer to the pressure switch could cause this.
How to Jump a Furnace Pressure Switch
All you’ll need to do this is a short jumper wire. You’ll often have an open switch you need to close when you jump it.
That shows the furnace must be turned on before the test can start, as a startup will be prevented if the switch installed is closed.
- Two or three wires should be visible entering your switch and access panel.
- One of the two wires from the pressure switch should be disconnected.
- Connect one end of your jumper wire to it.
- Turn on the furnace system and listen for the draft inducer to start.
- Connect the jumper wire’s other end to the pressure switch’s other wire.
- Allow a few minutes for it to run. Then, if there appear to be no issues, you can presume you need a new furnace pressure switch.
Remember that bypassing the pressure switch for troubleshooting is only a temporary setup.
It should not be used as a long-term setup. After all, this is a safety feature, and it’s not a good idea to overlook the dangers that a pressure switch guards against.
How to Fix a Combustion Air Switch that Has Failed to Close
If your combustion air switch didn’t close, the good news is that you can fix it. This section will give you some great ideas that you can use to help you fix your air switch.
If you need to use an air switch hose, you’ll need screwdrivers, flashlights, a multimeter, and maybe even a toolbox. You can see some of the steps below.
1. Turn Off the Power
First, you need to turn off the electricity. You should turn off the disconnect switch that you’ll find next to the furnace to do this. Switch off the breaker in your home service panel or breaker box if there’s no switch near your furnace.
2. Thoroughly Inspect the Rubber Hoses
The second step is to thoroughly check the rubber hoses. The first thing you need to do is remove the main access panel at the front of the furnace. It’s then time to look at the hose or the hoses that are attached to the air switch. Make sure they are well connected on both sides and in good shape.
In addition, you need to make sure the hoses aren’t blocked from the inside. However, don’t blow into the hoses while connected because it could damage the switch. So, think about using a cloth and a wire to clean. If any of them are broken, you might want to buy new ones.
3. Inspect the Port
Use the flashlight to look carefully at the port on the air switch and be very careful. Make sure they can be seen without any obstructions. Make sure this is the case, then use your screwdriver to remove any debris you’ll find inside.
Make sure you do it carefully to don’t damage the air switch body. Remember that you can’t blow into the inlet when you clean out the debris. When you’re done cleaning up the mess, reconnect the hoses.
4. Check the Furnace Cover
You should also check the ventilation slots on the furnace cover to make sure they are clean and sparkling clear. Remove any dirt and debris on the furnace cover when you check to see if it is there. The cover should also be changed.
5. Check the Vent Pipe for Any Obstruction
If you have a condensing type air switch, it’s essential to inspect the venting pipe for obstruction. Usually, the vent pipe is made from PVC material, and it stretches throughout the roof of your home and into the sidewalls.
6. Properly Test the Air Switch
Remove the wire connectors from the terminals of the wires connected to the air switch. If the air switch doesn’t work, use your multimeter to check it out. It’s important to touch the tester probe to any switch terminals and then record the reading.
The reading says 0 or is very close to 0. There’s no resistance when the reading is 0. This means your air switch is in good shape.
There are times when it’s important to think about replacing the air switch as soon as possible, even if the reading is higher than zero. I think you should call a professional to come and fix it for you. (Learn What To Do With Old Diesel Fuel)
7. Appropriately Test the Furnace
Before running the furnace, you need to connect the wires to the air switch and put the access panel back on the furnace. You should also fix the condensation trap to ensure that the furnace gases are properly caught and kept out of the air. After doing all of this, turn on the power to the furnace to see how it works.
Equipment is in good shape if you don’t see any mistakes. You can use it now. However, if you make mistakes, it’s important to get help from a professional.
What Is Air Proving Switch?
This is a switch with a body made of die-cast aluminum. It doesn’t have any parts made of plastic or tin. You can tell a lot about this switch because it’s long-lasting, and it can tell when there are small air pressures, vacuums, or changes in air pressure, so it’s good.
What Do I Do If My Pressure Switch Is Stuck Open?
The airflow switch is a safety device to ensure the combustion blower runs and delivers the correct air pressure for safe light off.
It can prove water flow and water pressure; it can measure flow.
The furnace goes into lockout mode until the pressure switch opens up in this switch.
If you see a pressure switch code and the inducer doesn’t work, take out one wire from the pressure switch and see if that helps. If the inducer is turned on, the pressure switch is stuck closed and can’t be opened.
What is an Airproving switch?
Air Pressure Proving Switches. Industrial grade pressure proving switches are made out of a die-cast aluminum body. The switches are used to detect small air pressures, vacuums, or changes in air pressure.
Why is the pressure switch stuck open?
A blocked pressure switch suggests an issue with the furnace’s operation. The plunger may not fully retract. You’ll need to clean the secondary exchanger and the inducer using a cloth and a wire brush.
How To Fix A Combustion Air Switch
Here’s how to fix pressure switches that won’t turn on.
- Turn Off The Power
- Examine Rubber Hoses
- Inspect the port.
- Examine Furnace Cover
- Check For Obstructions In Vent Pipe
- Test Your Air Switch
- Test Your Furnace