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What Causes a Furnace Pressure Switch To Fail?

Cassie Pound, owner of Quality Heating, Cooling, Plumbing & Electric
Published by
Cassie Pound
January 15, 2024
What Causes a Furnace Pressure Switch To Fail?

As you watch the temperatures plummet, you change your thermostat settings to heat. Your furnace works without a hitch for a while, producing cozy, warm air that heats your house despite the frigid weather outside. However, you inevitably stumble upon a frustrating obstacle that causes your furnace to stop working. At Quality Heating, Cooling & Plumbing, our HVAC contractors in Tulsa, Oklahoma, typically discover that a pressure switch failure triggers these sudden halts. What causes a furnace pressure switch to fail? Let’s dive into some answers below.

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What Exactly Is a Pressure Switch?

Pressure switches are safety features that prevent carbon monoxide exposure and explosions in households that use furnaces for heating. When negative motor pressure triggers their response, they automatically stop combustion. Your furnace needs combustion to produce the heat that warms your home.

The furnace completely shuts down when the switch interrupts the combustion process. While this feature ultimately protects your household from potential disasters, it also inconveniences you when the trigger doesn’t have potentially disastrous consequences. 

What Causes a Furnace Pressure Switch To Fail?

Furnace pressure switches can fail for myriad reasons beyond dangerous occurrences. Sometimes, a failure happens because of something innocuous. Regardless, only a qualified HVAC technician should diagnose the issue and verify whether any authentic threats exist. 

Learn more about some common causes of pressure switch failure below. Your HVAC technician might discover one of these reasons if your pressure switch fails. 

Diaphragm Flap Damage

The pressure switch houses a component called a diaphragm flap. This flap stays open when the furnace powers off. Once the unit powers back on, the flap closes to create a complete electrical circuit that allows electricity to power the furnace’s operations. 

Sometimes, this flap incurs damage or becomes stuck. Diaphragm flap damage prevents electricity from moving through its full, conductive path. Therefore, your pressure switch will fail, preventing your furnace from turning back on.  

Flue Obstructions

The flue pipe is a pathway that allows your furnace’s waste gasses to escape your system and home. These gasses can have toxic effects on household occupants if they maneuver back into the system through a process called back drafting. Therefore, the pressure switch will fail if it detects these gasses returning due to a lack of exit points. 

Flue obstructions are the most common cause of returning waste gas. Small animal carcasses, bird nests, and plant matter can sometimes become lodged into the flue pipe. An HVAC technician can remove these obstructions, allowing waste substances to escape again. 

Debris Buildup

The pressure switch is near the gas valve and ignition area on most energy-efficient residential furnaces. This location allows the switch to take fairly accurate readings of the gas and ignition environment. However, the switch can also gather dust and dirt buildup over time. 

The ignition area and gas valve create soot, which travels to nearby components. This soot can clog the limit switch, pressure switch, flame sensor, and pilot light. If any of these components becomes coated with too much debris, the furnace may struggle to operate.  

Old Age

What causes a furnace pressure switch to fail when all else seems fine? Like other parts, pressure switches eventually succumb to old age and wear. Fortunately, pressure switch replacement services don’t typically break the bank. 

A licensed HVAC technician can quickly and efficiently perform this service. If you lose heat due to a faulty, old pressure switch, they’ll help you enjoy a cozy indoor environment again in no time. 

Malfunctioning Pressure Switch Hoses

Many pressure switches have one or two hoses connected to them. These hoses attach the switch to the condensate collector box and the draft inducer. Sometimes, the hoses become obstructed with debris. 

The hose that connects to the condensate collector box may become flooded with condensation. Meanwhile, the one attached to the draft inducer might collect too much dust and other dry debris. An HVAC technician will detach the hoses and remove any detritus hidden within their length. Otherwise, they may replace them. 

Electrical Disconnections

If you recently experienced a power surge or other electrical phenomena in your area, you can likely blame pressure switch failures on these occurrences. Surges overwhelm the pressure switch alongside other components. Your technician will probably replace the switch under these circumstances. 

Disconnected wires may also trigger failures. Like other furnace networks, the pressure switch relies on electrical circuits to send messages and respond to its environment. Loose connections are common culprits of switch failures. 

Preventing Pressure Switch Failures

What can you do to avoid pressure switch failures? Choosing reputable HVAC services throughout the lifespan of your furnace will significantly decrease the odds of misreadings and triggers causing failures. Implement the tips outlined below to protect your pressure switch and furnace. 

Choose Reputable Installation Services

Furnace installation is the foundation for a successful service life. Subpar installation services from unqualified contractors will result in various shortcomings and disappointments. A poorly installed furnace is more likely to develop triggers that cause pressure switch failures and other impromptu annoyances at the worst possible times. 

Regular Professional Maintenance

Scheduling annual maintenance appointments with a professional HVAC company will mitigate most of the above-listed issues. A technician will examine and troubleshoot your furnace for issues like dirty components, flue obstructions, and damaged parts. If they discover these problems, they’ll address them during the service. 

Maintenance services are the best way to keep components clean and intact. Not only do they prevent inconvenient failures, but they also prolong your furnace’s service life. You’ll enjoy reliable, complication-free heating when you schedule your yearly appointment in the autumn. 

Choose Furnace Repair and Maintenance Services From Quality Heating, Cooling & Plumbing

What causes a furnace pressure switch to fail without warning? Damaged or dirty components, regular wear and tear, and electrical disconnections are some of the most common switch triggers. Quality Heating, Cooling & Plumbing also answers other pertinent HVAC questions, including, “Is it bad to turn your furnace on and off?

Accompany the answers to your burning heating and cooling inquiries with reputable HVAC services in Tulsa, Oklahoma, and surrounding areas. Call (918) 393-4577 to schedule services.

Cassie Pound, owner of Quality Heating, Cooling, Plumbing & Electric
Published by
Cassie Pound

Cassie Pound is the Vice President of Quality Heating, Cooling, Plumbing & Electric with locations in Tulsa, Glenpool, and Bartlesville, Oklahoma.