What Happens When a Furnace Pressure Switch Goes Bad
Is your furnace blowing but not producing any heat? You might have a faulty pressure switch, but before you search "What happens when a furnace pressure switch goes bad?" keep reading.
Repairs and heating installation by Bates Air and Heat are the best in the area! Call 722-773-6926 to schedule an appointment today.
What Is the Pressure Switch?
When you turn on the heat, your entire HVAC system works in complicated ways behind the scenes to deliver heat throughout your house. The first step is your thermostat sending a signal to your furnace to activate it. Then, the inducer motor blows out any excess gas before starting the furnace.
When the exhaust exits, it creates negative pressure, which signals the pressure switch to close to prevent dangerous combustible gases from igniting. Thus, the pressure switch is an important safety component.
When your pressure switch malfunctions, your furnace might not start, preventing a host of dangerous situations. Sometimes, it starts but won't provide heat.
Signs Your Pressure Switch Is Bad
What happens when a furnace pressure switch goes bad? While your furnace can still run, you won't use any gas. Look for the following signs to determine your problem with the switch.
No Hot Air
The most common problem with a faulty pressure switch is a lack of hot air. This occurs when your furnace runs, but the pressure switch doesn't allow the gas to ignite. If you notice lukewarm air filling your house, the pressure switch might be the culprit!
Check the Control Panel
Many modern furnaces include a control board with an LED light that indicates when the pressure switch fails. The right error code shows the switch is open, forcing the furnace into safety lockout mode.
Unusual Noises
If your furnace makes unusual noises, it could mean your pressure switch is failing to start. You might hear the inducer motor clanking or grinding, your problem might not be the pressure switch.
You can also determine if the pressure switch is working by listening for the gas valve to click on. If it clicks on, the problem is probably the igniter and not the pressure switch.
Cycling
When your furnace turns on, and off rapidly, regardless of temperature settings, it means the furnace is attempting to start but can't. While the problem could be any of several issues, your pressure switch is a good place to start!
Common Pressure Switch Problems
What causes your pressure switch to fail? The following are the most common causes.
Age
No matter the appliance, old age always comes with frequent mechanical failure. Concerning your pressure switch, old age can cause it to take incorrect readings or cycle the furnace.
Electrical Problem
Several electrical problems can prevent your pressure switch from working correctly. Electrical shorts or surges are common if your wiring is bad or out of date or with loose or faulty connections.
Damaged and Loose Components
Several components within your furnace are vulnerable to damage or loosening over time, preventing your pressure switch from working correctly.
The suction hose or diaphragm often becomes damaged or stuck, requiring maintenance to ensure your furnace has access to gas. Likewise, the inducer fan frequently breaks or blows too slowly, preventing the exhaust from exiting the furnace and preventing the pressure switch from sensing the negative pressure.
Dirt and Debris
Dirt and dust can build up on the switch, preventing it from accurately reading the pressure. Dirt and debris can also block the inducer fan from running efficiently.
Blocks and Clogs
Blockages can occur in numerous places throughout the system. One of the most frequent places is in the chimney or flu, especially in the warmer months when birds or animals can crawl in and get stuck. In this case, you'll likely see the block and can remove it yourself.
The opening leading to the collection chamber can also clog, preventing the switch from accurately reading the pressure.
Water Problems
Water can build up in several areas in your furnace, including the inducer fan housing and the switch hose. If the problem is in the hose, you can drain it to restore your switch to working order.
Diagnosing Pressure Switch Problems
While an HVAC professional can easily diagnose problems with your pressure switch, you can run several tests to verify the problem before you contact them.
After you check the flue for blockages and listen for the gas valve to click on, you can confirm it's the pressure switch with a voltmeter. Turn the power off and remove the wires from the pressure switch. If it measures close to zero, the switch is closed and needs replacement.
Replacing Your Pressure Switch
How does your HVAC professional replace your pressure switch? They follow these steps:
- The HVAC specialist should always turn off the power to your unit.
- After the power's disconnected, the technician disconnects the wires and hose from the pressure switch.
- The service specialist removes the switch from its mounting bracket. In some cases, they replace the bracket with a new one.
- They remount the new switch and reconnect the hose and wires.
- After they restore power, they'll test the unit to verify the new pressure switch works as intended.
Pressure switches are specialty items, meaning you can't usually find them in home improvement stores to replace them yourself. While the piece itself is very affordable because your furnace is complicated and the pressure switch is important for safety, always call Bates Air & Heat LLC for replacement.
Call Bates Air & Heat LLC for All Your Furnace Repairs
Now that you know what happens when a furnace pressure switch goes bad, you can address the issue by calling for a replacement. Whether you need a new pressure switch or want to replace the furnace and AC at the same time, our team at Bates Air & Heat LLC is here to help.
Call our furnace experts at 722-773-6926 to schedule an appointment today and ensure your home stays comfortable year-round.












