How to Fix Furnace Pressure Switch Stuck Open: A Comprehensive Guide

How to Fix Furnace Pressure Switch Stuck Open A Comprehensive Guide

How to Fix Furnace Pressure Switch Stuck Open: A Comprehensive Guide


A malfunctioning furnace can be a major inconvenience, especially during the cold winter months. One common issue that homeowners encounter is a furnace pressure switch that is stuck open. This problem can lead to your furnace not working properly or not turning on at all. In this article, we will provide you with a step-by-step guide on how to fix a furnace pressure switch that is stuck open.

Understanding the Furnace Pressure Switch

Before we dive into the troubleshooting steps, it’s essential to understand what a furnace pressure switch is and its role in your heating system.

What Is a Furnace Pressure Switch?

A furnace pressure switch is a safety device designed to ensure that there is adequate airflow in your furnace before it ignites. It senses the air pressure in the furnace’s combustion chamber and ensures that it’s safe to proceed with the ignition process.

Why Does It Get Stuck Open?

Several factors can cause a furnace pressure switch to get stuck open. Dust and debris buildup, a malfunctioning switch, or issues with the venting system can all contribute to this problem.

Tools You’ll Need

Before you start troubleshooting and fixing the issue, gather the following tools and materials:

  1. Screwdriver
  2. Multimeter
  3. Soft brush
  4. Replacement pressure switch (if necessary)

Step-by-Step Guide to Fixing a Furnace Pressure Switch Stuck Open

Now, let’s go through the process of troubleshooting and fixing a stuck open furnace pressure switch.

Step 1: Safety First

Before you begin any work on your furnace, ensure it is completely powered off. Turn off the electrical supply and gas valve to the furnace.

Step 2: Locate the Pressure Switch

The pressure switch is typically located near the draft inducer motor. It’s a small, round device with two or three wires connected to it.

Step 3: Inspect for Blockages

Inspect for Blockages

Inspect the tubing and ports connected to the pressure switch for any blockages or obstructions. Use a soft brush to clean away any dust or debris that may be causing the switch to malfunction.

Step 4: Test the Switch

Use a multimeter to test the continuity of the pressure switch. Disconnect the wires from the switch and place the multimeter probes on the terminals. If the switch fails the continuity test, it may need to be replaced.

Step 5: Replace the Pressure Switch (if necessary)

If the pressure switch is found to be faulty during testing, you may need to replace it. To do so, follow these steps:

  1. Purchase a Replacement: Begin by acquiring a replacement pressure switch that matches the specifications of your furnace model. You can find this information in your furnace’s user manual or by consulting with a professional HVAC technician.
  2. Disconnect Wires: Carefully disconnect the wires from the terminals of the old pressure switch. Be sure to take note of their positions or take a photo for reference.
  3. Remove the Old Switch: Unscrew and remove the old pressure switch from its mounting bracket or location. Keep any screws or mounting hardware for the new switch.
  4. Install the New Switch: Position the new pressure switch in the same location as the old one and secure it with the provided screws or mounting hardware. Ensure it is securely in place.
  5. Connect Wires: Reconnect the wires to the corresponding terminals on the new pressure switch, following the reference you made earlier.

Step 6: Reassemble and Test

After replacing the pressure switch (if necessary), it’s time to reassemble the components you may have removed during the process. Make sure that everything is securely in place and properly reconnected.

Now, you can proceed to test your furnace to see if the issue has been resolved:

  1. Turn On Electrical Supply: Turn on the electrical supply to your furnace.
  2. Open Gas Valve: Turn on the gas valve to the furnace.
  3. Test the Furnace: Adjust your thermostat to call for heat and observe the furnace’s operation. Listen for the sound of the inducer motor and watch for any error codes on the furnace control board. If the furnace ignites and operates normally, the issue is likely resolved.

Step 7: Regular Maintenance

To prevent future issues with your furnace pressure switch, it’s essential to schedule regular maintenance checks. Here are some tips for ongoing maintenance:

  • Change the Air Filter: Regularly replace or clean the air filter in your furnace. A clogged filter can lead to airflow problems, which may affect the pressure switch.
  • Keep Vents and Flues Clear: Ensure that the vents and flues in your heating system are free from obstructions and debris.
  • Schedule Professional Maintenance: Consider scheduling an annual maintenance service with a qualified HVAC technician. They can thoroughly inspect and clean your furnace, including the pressure switch, to keep it in optimal condition.


Dealing with a furnace pressure switch stuck open can be frustrating, but with the right knowledge and tools, you can resolve the issue safely and effectively. Remember always to prioritize safety when working with your furnace, and if you’re unsure about any step, consult a professional HVAC technician.


Can I clean the pressure switch myself?

Yes, you can clean the pressure switch yourself by following the steps outlined in this article. However, if you’re not comfortable doing it, it’s best to hire a professional technician.

How often should I schedule furnace maintenance?

It’s recommended to schedule furnace maintenance at least once a year to ensure it operates efficiently and safely.

Are there any other reasons why my furnace may not be working?

Yes, there could be various reasons, such as a faulty thermostat, a clogged air filter, or a malfunctioning ignition system. It’s essential to diagnose the specific issue correctly.

Can a stuck open pressure switch be dangerous?

While it can disrupt your furnace’s operation, a stuck open pressure switch is primarily a safety feature. It prevents the furnace from operating when there’s insufficient airflow, which could be dangerous.

Is it possible to prevent the pressure switch from getting stuck open in the first place?

Regular maintenance and cleaning can help prevent the pressure switch from getting stuck open. Additionally, ensuring proper venting and airflow in your furnace system can reduce the likelihood of this issue occurring.

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