A furnace has several safety components working quietly in the background to keep your home warm and safe. One part that often goes unnoticed is the furnace pressure switch. While small, this pressure switch works with other furnace components to ensure your heating system operates correctly and doesn’t pose hazards.
In this guide, we’ll look at what a pressure switch does, how it helps furnace operation, why it matters for safety, signs it may be failing, basic cleaning, repair, installation concerns, and when to call heating professionals like Tegridy Air in Kenner, Louisiana.
This information is especially helpful for homeowners curious about their gas furnace or anyone noticing trouble with their furnace starting or staying on.
What Is a Furnace Pressure Switch?
A furnace pressure switch is a safety control device located near the draft inducer motor. Its job is to detect whether the furnace has proper airflow before the burner ignites. The pressure switch works closely with the inducer to confirm safe venting.
When your furnace starts, the pressure switch checks that harmful gases move safely outdoors. If proper air pressure isn’t detected, the switch prevents the burner from lighting. This protects your home from unsafe situations such as gas leaks, poor venting pressure, or carbon monoxide buildup.
So even though it’s small, this safety switch is central to safe furnace operation.
Why the Pressure Switch Matters
Your gas furnace releases combustion gases during operation. These must exit through the furnace venting system. The pressure switch detects safe airflow before burners ignite. If airflow is weak or unsafe, the switch opens, stopping the heating cycle.
It helps ensure:
- Combustion gases do not build up
- Exhaust leaves through the vent
- Furnace runs only when safe
If the pressure switch isn’t satisfied, it shuts down the furnace to protect your home.
How a Furnace Pressure Switch Works
When your thermostat calls for heat, the inducer motor or draft inducer starts moving exhaust and outside air through the vent. This creates negative pressure.
The pressure switch senses this draft pressure. If the pressure is correct, the switch closes, signaling the control board that it’s safe to begin heating. Burners ignite, warm air flows, and your heating system runs normally.
If airflow is blocked or weak, the switch remains open. The furnace running will stop to prevent unsafe operation. If the problem continues, the furnace typically shuts down and shows an error.
The pressure switch is one of the most important furnace safety devices.
Types of Furnace Pressure Switches
There are several types of pressure switches depending on the type of furnace or efficiency rating. A conventional furnace may have one pressure switch, while a high-efficiency model may have two hoses on the pressure switch or multiple switches.
- Single pressure switch
Most standard furnaces have one pressure switch. - Two-stage / multi-stage switches
Common in higher-efficiency units. - Electronic pressure switches
Used in advanced furnace models and heating and cooling systems.
Even though designs vary, all ensure safe airflow before ignition.
Signs of a Bad Furnace Pressure Switch
A bad pressure switch or malfunctioning pressure switch often shows symptoms early in the cycle:
- Furnace starts then shuts off quickly
- Furnace won’t ignite
- Switch can’t close
- Repeated clicking
- Error code flashes
- Pressure switch remains open
- Burning smell or airflow changes
- Furnace short cycling
A faulty pressure switch can cause your furnace to stop heating or prevent operation.
What Causes Pressure Switch Problems?
A pressure switch might fail due to the switch itself or related issues. The pressure switch could malfunction when the inducer or vent isn’t working properly.
Common causes of pressure switch failure:
- Blocked vent or blocked exhaust
- Switch and the inducer not operating correctly
- Clogged hoses on the pressure switch
- Loose tubing
- Excess moisture
- Blockage in intake or vent
- Furnace vent problems
- Old furnace components
- Bad switch
- Problems with inducer motor
- Issue inside the switch
A blocked vent or failing inducer can easily cause your furnace to shut down as the pressure switch keeps opening.
Diagnosing a Faulty Furnace Pressure Switch
Common signs include difficulty starting, repeated attempts, and no heating. Many modern units show error codes helpful for troubleshooting.
A visual inspection can reveal:
- Moisture
- Cracks
- Loose tubing
- Furnace components damage
A professional may:
- Test voltage
- Inspect venting
- Check the furnace tubing
- Evaluate air pressure
- Inspect the furnace exhaust system
Because it involves electricity, gas, and heating system risks, expert service is recommended.
Can You Bypass a Furnace Pressure Switch?
Some try to bypass the switch, but doing so is extremely unsafe. It eliminates protections meant to prevent gas furnace hazards, including carbon monoxide exposure.
Bypassing:
- Violates safety codes
- Risks pressure switch failure
- Can allow dangerous natural gas or propane buildup
- May void warranties
Instead of bypassing, call a pro to inspect the pressure switch and decide if cleaning, repair, or installation of a new pressure switch is needed.
How Professionals Repair Pressure Switch Problems
A malfunction doesn’t always require replacement. Sometimes, repair or cleaning solves the issue.
A technician may:
- Clear a blocked vent
- Test the draft inducer
- Clean tubing
- Perform furnace repair
- Replace the pressure switch if needed
If replacing a furnace pressure switch is necessary, installation is typically simple and same-day.
Maintenance Tips to Prevent Issues
Regular cleaning, annual furnace care, and basic upkeep lower the chances of pressure switch issues and furnace pressure switch fails.
Best practices:
- Annual furnace check
- Keep vents clear
- Change filters
- Respond to unusual noises
- Monitor heating and air conditioning performance
Good maintenance improves usable life and supports indoor air quality.
What Does a Furnace Pressure Switch Cost?
Cost varies by furnace models, labor, and type of switch. Delaying repair can worsen issues, affecting ignition or ventilation.
When To Call Tegridy Air
If your pressure switches seem unstable or you notice short cycling, call a trained HVAC professional. Tegridy Air offers:
- Troubleshoot support
- Full furnace repair
- Pressure switch installation
- Seasonal tune-ups
- Cleaning and inspection
Whether dealing with a failing pressure switch or any furnace questions, a trained technician can help restore safe performance.
Final Thoughts
The furnace pressure switch is small but essential. If the switch is stuck open position, or pressure within the venting path is off, it may stop operation to protect your home. If the switch won’t close, or switch also detects poor pressure, it may shut the furnace down.
Taking care of your heating and air conditioning equipment, performing annual tune-ups, and staying aware of symptoms help prevent breakdowns.
