How To Bypass A Pressure Switch On A Furnace? Essential Tips

Understanding The Pressure Switch On A Furnace. 

The Pressure Switch is vital for a furnace to run safely. It checks the air pressure created by the motor. 

How To Bypass A Pressure Switch On A Furnace

This table can help you understand it better:

Column 1Column 2
PurposeFurnace safety.
Location on FurnaceNear Motor or Fan.
How it WorksCheck air pressure.
Open/Close SwitchNegative Pressure closes the switch.
ImportancePrevents Carbon Monoxide leaks.

It’s important to note that if the Pressure Switch isn’t working, your furnace may not start. Or it could cause safety issues, like carbon monoxide leaks. Don’t bypass it as a temporary solution until help arrives.

In some cases, blockages or other issues may make the switch stay open, even with normal pressure. This is dangerous and can lead to harmful gases leaking from your furnace. If this happens, call an HVAC technician without delay!

Don’t let furnace problems due to Pressure Switch malfunctioning worsen. 

Contact a senior tech or repair technician immediately to prevent hazardous events.

Reasons To Bypass A Furnace Pressure Switch.

Bypassing a furnace pressure switch may be necessary to diagnose and fix underlying issues. 

Here are some reasons why:

  1. Blockages: Obstructions in the air intake or exhaust vent can trigger the switch. Bypass it to pinpoint the blockage.
  2. Faulty Switch: Is the switch not signaling the inducer motor to start? Bypass it to confirm.
  3. Safety hazard: Blocked flue pipe causing carbon monoxide leak? Bypass to check.
  4. No Professional Assistance: No help available or too expensive? Bypass as a temp solution.

Note that bypassing should only be done by certified HVAC technicians with experience. Improper handling risks electrocution and fire.

If problems come up while examining your furnace, here are some tips from our senior techs at Climate Control:

  • Debris in the hose connecting Pressure Switch Process Port to Inducer Fan? Cut power, clean out material, then examine with an open port.
  • No voltage recorded? Try jumping two terminals on the control board with alligator clips. Tighten key fixtures and screws so no hum or whistle during operation.
  • Minimal pressure? Measure suction with a negative meter or identify a faulty inducer fan motor.

These suggestions should help you solve furnace problems. 

Remember, if unsure, seek professional help!

Ways To Bypass Pressure Switch On A Furnace.

To temporarily bypass a pressure switch on a furnace, certain steps need to be followed for safety reasons. 

Here is a professional guide on how to bypass a pressure switch on a furnace:>

  1. Locate the Pressure Switch: The pressure switch is usually located near the inducer motor. It is a small part with a hose connected to it. Use a voltage meter to make sure the power is disconnected from the furnace.
  2. Check for Blockages: Ensure that there are no blockages in the port or water in the hose connected to the switch. If there is, remove the blockage, or replace the hose.
  3. Bypass the Switch: Locate the switch’s wires and remove them from their terminals. Connect the two wires with a jumper to bypass the switch. After the bypass is installed, reconnect the furnace power and turn it back on.
  4. Test the System: Test the furnace and monitor it for a short while to ensure that everything is working well.

It is important to note that bypassing the pressure switch is only a temporary solution. It is not a permanent fix and professional assistance should be sought. Neglecting furnace maintenance can lead to serious safety issues, including carbon monoxide poisoning.

If you encounter any problems or have any concerns, it is wise to call an HVAC technician. They have the knowledge and tools to repair and replace parts safely and effectively.

Remember, safety should always be a top priority when dealing with furnace issues. Do not attempt any job in the world of HVAC that you are not qualified for.

Time to use your detective skills and channel your inner Sherlock to solve the case of the blockage or draft problem in your furnace.

Checking for Blockage or Draft Problems.

Checking for air blockages or draft problems is essential for furnace maintenance. The flow of air must be steady for your furnace to work properly and safely.

 Here are some ways to detect issues, without calling a pro:

  • Inspect air filters. Dirty filters can cause blockages and reduce airflow. Clean or replace if needed.
  • Check air vents. Make sure they’re clear of furniture, carpets, and curtains.
  • Examine the exhaust vent outside. Make sure it’s free of debris like leaves, snow, or animal nests.

Don’t just check once; inspect your furnace regularly. Plus, make sure all areas around your furnace are free of clutter. Otherwise, your furnace may be at risk of dangerous carbon monoxide levels.

My neighbor experienced a problem when they blocked a vent in their basement with boxes. This created a restriction in airflow, causing issues with their heat exchange system. 

So be careful and inspect for blockages, and ensure proper ventilation throughout your house with these tips!

Testing Voltage and Resistance of the Switch.

To ensure a furnace runs efficiently, test the pressure switch voltage and resistance. 

Here’s a 5-step guide:

  1. Turn off the power to the furnace.
  2. Locate the pressure switch near the blower.
  3. Use a multimeter to test voltage. Low readings or no voltage indicate wiring faults or a malfunctioning transformer.
  4. Check the resistance with an ohmmeter. Look for zero ohms when closed, and infinite resistance when open.
  5. Replace broken parts per manufacturer instructions.

Pro Tip: Always read the manufacturer’s manual before bypassing or replacing components. 

Incorrect installation can damage the furnace, reducing its lifespan and leading to expensive repairs.

Using a Jumper to Bypass the Pressure Switch.

Got a furnace with pressure switch problems? No worries! Jump it by using a wire. 

Here’s how:

  1. Turn off your furnace completely.
  2. Locate the pressure switch. Look for two terminals; one labeled “NC” and one labeled “C”.
  3. Connect a wire between these two terminals. This creates a bypass and can get the furnace running again.
  4. Turn on the furnace. If it works, remove the wire after using it.

This is only a temporary fix. Professional help is needed to diagnose and repair any long-term issues.

Be sure to use insulated wire and be aware of safety hazards. 

Handle electrical components with caution; do not attempt if you are not comfortable.

Creating a Temporary Solution to Bypass the Switch.

Dealing with a faulty pressure switch on your furnace? As a quick fix, follow these six easy steps to create a temporary bypass solution.

  1. Locate the switch and remove the wires.
  2. Connect them securely.
  3. Insulate each wire with electrical tape or a wire nut.
  4. Turn on the furnace and check for any faults.
  5. Let it run for five minutes and look for any irregular signs.
  6. When it’s all good, turn it off, reattach the wires, and get a proper repair job.

This temporary solution will give you time until you can get a professional repair. But be careful! The heat exchanger may overheat if the override is unnoticed, leading to potential danger. 

So, if it all feels overwhelming, don’t hesitate to call in the pros. They provide long-term solutions, avoiding safety hazards and protecting your device’s warranty.

Safety first; remember, burnt eyebrows are never in style!

Safety Measures To Consider Before Bypassing Pressure Switch On Furnace 

In this section, we will discuss safety measures that one should consider before attempting to bypass a pressure switch on a furnace. 

It is essential to keep in mind that tampering with safety features can be dangerous if not done correctly.

Here is a 4-step guide to follow before bypassing a pressure switch:

  1. Before any repair or maintenance work, one should turn off the power supply to the furnace.
  2. An HVAC technician or a professional should perform this job. Attempting to do it oneself may lead to electrocution and other hazards.
  3. One should check the furnace’s ventilation system for any blockage or obstructions that may cause negative pressure and trigger the pressure switch’s open position.
  4. Use a voltage meter to test the wires and terminals. Ensure to use proper personal protective equipment during this process.

Finally, as a pro tip, we suggest that if you are not sure about how to bypass a pressure switch, get professional assistance. It is always better to be safe than sorry.

Pressure switches are like your ex, they only work when you don’t want them to.

Understanding the Safety Feature of a Pressure Switch.

Pressure switches are an essential safety feature in many mechanical systems. They keep the system in a safe range of pressure and protect people and equipment from harm.

 Before bypassing a pressure switch, understand safety measures.

  1. Have a valid reason to bypass it. Otherwise, don’t.
  2. Shut down the power supply and decompress the system.
  3. Use good tools with technical personnel.
  4. Install alternative control mechanisms that are as safe as the original equipment.

Lastly, test and verify all control measures for compliance. Re-energize the system only if everything is okay.

Pro Tip: Know and analyze risks before bypassing a pressure switch. Otherwise, it may cause harm. 

And don’t forget to check your carbon monoxide detector; it’s like getting a surprise visit from the Grim Reaper!

Checking for Carbon Monoxide Leaks.

Carbon monoxide is an invisible gas that can have serious health impacts if not detected. Check for leaks when bypassing a pressure switch!

Steps to ensure safety:

  1. Set up carbon monoxide detectors near fuel-burning appliances.
  2. Check vents and chimneys for proper ventilation.
  3. Monitor symptoms such as headaches, nausea, and dizziness.
  4. Get fuel-burning appliances serviced regularly.

You may not see any signs of a leak, but preventive measures are essential. Detectors, monitoring symptoms, and regular maintenance can help.

Pro tip: Regular servicing can prevent costly repairs. 

Don’t be a DIY disaster; seek help if needed!

When To Seek Professional Assistance To Bypass Pressure Switch On Furnace. 

When it comes to furnace pressure switch troubleshooting, caution is key. If unsure about being able to diagnose and repair the issue, professional help is best

Malfunctions can lead to an inducer motor not starting and carbon monoxide leaks. Electrical work and testing equipment may be able to identify and address wiring and voltage issues. But, weigh the risks and rewards of DIY repairs. Your safety is a top priority.

 If you have any doubts, get help from a licensed HVAC technician. According to a senior tech at One Hour Heating & Air Conditioning, “In most cases, replacing parts of a cannon-port assembly with diaphragm & tubing, along with a combustion air inducer fan is better than trying to identify the cause.” 

Remember, bypassing a pressure switch is only temporary.

Frequently Asked Questions. 

Q1: Why would I need to bypass a pressure switch on a furnace?

A: Bypassing a pressure switch on a furnace may be necessary in certain situations, such as troubleshooting or temporary troubleshooting when the switch is malfunctioning or causing issues with the furnace’s operation.

Q2: What is a pressure switch on a furnace?

A: A pressure switch on a furnace is a safety device that monitors the pressure in the combustion chamber or venting system. It ensures that the furnace operates within safe parameters by confirming the presence of sufficient airflow or proper venting.

Q3: Is it safe to bypass a pressure switch on a furnace?

A: Bypassing a pressure switch should only be done as a temporary measure for troubleshooting purposes. It is not recommended to bypass a pressure switch permanently as it compromises the safety features of the furnace and may lead to unsafe operation.

Q4: How can I locate the pressure switch on my furnace?

A: The pressure switch is typically located near the burner assembly or the blower motor assembly. Consult your furnace’s manual or contact the manufacturer for specific instructions on locating the pressure switch in your particular furnace model.

Q5: What are the steps to bypass a pressure switch on a furnace?

A: Bypassing a pressure switch requires caution and should only be done temporarily. Here are the general steps:

  • Ensure the furnace is powered off and disconnected from the electrical supply.
  • Locate the pressure switch on your furnace.
  • Disconnect the wires connected to the pressure switch terminals.
  • Connect these wires using a jumper wire or an appropriate connector.
  • Insulate the exposed ends of the bypassed wires using electrical tape or wire connectors.
  • Restore power to the furnace and test its operation, but remember this should only be a temporary troubleshooting measure.

Q6: When should I contact a professional instead of bypassing the pressure switch myself?

A: Bypassing a pressure switch should be considered a temporary troubleshooting measure. If you are unsure about the process, lack experience with furnaces, or if the pressure switch continues to cause problems after bypassing, it is strongly recommended to contact a qualified HVAC technician. They have the expertise to diagnose and fix the underlying issue safely and efficiently.


After trying the steps to bypass a pressure switch on a furnace, it may start up right away. However, it is still best to get help from a pro. Remember, safety matters most. Furthermore, some things weren’t mentioned before. If the pressure switch is blocked by something in the vent or flue pipe, taking away the blockage will do the job and you won’t have to bypass the pressure switch. But, without proper knowledge or experience, it could be dangerous and could cause more damage.

A pro tip: Before doing furnace maintenance, always check for carbon monoxide. Use a carbon monoxide meter for your safety.