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What Do These Furnace Error Codes Mean?

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What Do These Furnace Error Codes Mean?

Posted On: September 21, 2024

What Do These Furnace Error Codes Mean?

Furnace error codes are diagnostic signals that help identify problems with the furnace's operation. Each code represents a specific issue that needs to be addressed, typically related to components like the thermostat, sensors, or burners. Here's a breakdown of some common furnace error codes:


1. Error Code 1 Flash:

  • Issue: Furnace is in a lockout mode.
  • Meaning: This typically happens after three failed ignition attempts. The furnace will shut down for safety reasons.
  • Solution: Reset the furnace or call a technician to check the ignition system.

2. Error Code 2 Flashes:

  • Issue: Pressure switch stuck closed.
  • Meaning: The pressure switch monitors the venting system. If it’s stuck, it means the furnace might be having issues with the venting process.
  • Solution: Check for blockages in the vent pipe or replace the pressure switch.

3. Error Code 3 Flashes:

  • Issue: Pressure switch stuck open.
  • Meaning: The switch is open when it should be closed during normal furnace operation.
  • Solution: Ensure the vent pipes are clear, and the switch is functioning properly.

4. Error Code 4 Flashes:

  • Issue: Limit switch open.
  • Meaning: The limit switch is a safety device that shuts off the furnace if it overheats.
  • Solution: Check for restricted airflow due to dirty filters or obstructed vents.

5. Error Code 5 Flashes:

  • Issue: Flame sensor failure.
  • Meaning: The furnace cannot detect a flame, which could indicate a dirty or faulty flame sensor.
  • Solution: Clean the flame sensor or replace it if necessary.

6. Error Code 6 Flashes:

  • Issue: Ignition lockout.
  • Meaning: After three failed ignition attempts, the furnace will enter lockout mode.
  • Solution: Check the gas supply and ignition system, and reset the furnace.

7. Error Code 7 Flashes:

  • Issue: Gas valve stuck closed.
  • Meaning: The furnace cannot get the gas needed for combustion.
  • Solution: Inspect the gas valve and ensure it’s operating correctly.

8. Error Code 8 Flashes:

  • Issue: Low voltage issue.
  • Meaning: The furnace is not receiving adequate power to function properly.
  • Solution: Check the electrical connections and wiring to the furnace.

Each brand of furnace may have different error codes, so it's important to refer to the furnace’s manual for specific meanings or call a professional HVAC technician if you're unsure about any particular code.



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by Bill, Oshawa on Twintech Heating and Cooling

We are very happy with our new furnace. The service was excellent the guys worked 6 hours straight through and there was no mess at all they took the old furnace box’s etc with them they then explained everything to us they were very helpful and pleasant , when we need a new air conditioner we know who to call!

by Ken, Bomanville on Twintech Heating and Cooling

The crew from sales to installation was very professional and had great attention to detail

by Tracy, Pickering on Twintech Heating and Cooling

We couldn’t have been more impressed with Twintech - from our first service call with Mitch who took the time to thoroughly diagnose the issue with our furnace, to Dave who proposed a well thought out solution to meet our needs and finally Greg and team who acted quickly to install given we had no heat.


We did our due diligence by soliciting quotes from alternate providers and were shocked and disappointed by the aggressive and manipulative tactics used.


Twintech was honest in their approach, detailed in their product knowledge, reasonably priced, diligent in their follow-up and valued our business.


Well done Twintech! You made this a positive experience for us and our new furnace works beautifully!

by Skapoor, Ajax on Twintech Heating and Cooling

We recently purchased an Amana high efficiency furnace and humdifier through Twintech. The work was completed very professionally and the quality of the workmanship was high. There was some additional sheet metal work required to complete the installation, which they were able to complete themselves. Overall I am very pleased with the work and would highly recommend Twintech for a furnace replacement.

by Steve, Oshawa on Twintech Heating and Cooling

We were very pleased with every aspect of the work that was done. They were very professional and polite. They arrived when they said they would and job was completed on estimated time


We would highly recommend them to whoever needed a recommendation


We have a very large dog and they were very understanding and respectful of him being around

by Patrick, Toronto on Twintech Heating and Cooling

The blower on our furnace stopped working leaving us with a cold house. Dave from TwinTech responded immediately to our HomeStars service request. From beginning to end Dave was nothing but helpful, friendly and professional, he did a great job of walking us through the quote and scope of work.


The replacement of the furnace went smoothly. The Guys did a great job, everyone was very friendly and polite. There were no hiccups, or unexpected costs. The only surprise was they left the work area cleaner than it was before they started.


Was a great experience with the whole TwinTech team. Its been a couple of months since the new furnace has been installed and its working great!

by Ed, Whitby on Twintech Heating and Cooling

I heard about TwinTech when researching new furnaces at furnaceprices.ca. After contacting them about my broken down furnace, Dave came to my house the next day to assess my situation and requirements for a new furnace. He recommended one that had stainless steel heat exchangers which sold me since my previous furnace had issues with a rusted secondary heat exchanger that had to be replaced. Dave also set me up with an appointment with an energy audit company so that I could take advantage of a rebate to help improve the energy efficiency of my home and get some money back. A few days later, Greg, Grant, and Mitch came to install the new furnace and remove the old one. When delivering and removing the furnaces, they were very careful not to damage my floors and walls, and even laid out red carpeting to protect the floors. They were very friendly and professional. The installation was completed in the time they said it would take and they cleaned up their work areas. Within a week, Dave called to follow-up to see how everything was going. I have already recommended them to several friends and family members who may need new furnaces soon.

by Fred, Toronto on Twintech Heating and Cooling

Twintech did a great job, from Dave the Sales Rep to the Office staff and The Professional Technicians who did the installation. They were professional, courteous, knowledgable and informative. From beginning to follow up we were completely satisfied with everything. Thanks Again. Sincerely The Laytons

by Elle, Oshawa on Twintech Heating and Cooling

Great product, great service, great follow-up. The Twintech Heating and Cooling arranged removal of my existing oil tank and they installed the new gas furnace Amana (made in USA). I am very happy with the final result and support I received throughout the process. My thanks go to the entire Twintech team for their professionalism, great communication and follow-up.

by John & Linda, Ajax on Twintech Heating and Cooling

We've had Twintech provide us with work in the past, for an inground pool heater and required rough-in for a new gas stove. More recently they provided the same friendly, professional, timely and clean installation of our new furnace.

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by Aaron on Twintech Heating and Cooling

We are very happy to recommend this company to everyone. Our furnace broke down on Sunday morning. We phoned them and before noon Grant the owner showed up. He worked on the furnace for about a hour not wanting to give up to fix the problem. The furnace was 17 years old. I was the one talking about replacing it. End result was the next day it was all done. On the Sunday Bob came over with heaters to warm up the house. We decided to replace the water heater at the same time. Thanks Grant for the excellent work. Thumbs up.

by Linda on Twintech Heating and Cooling

Right on time. Explained how to work the HRV in a different way so the house would not be so dry. Changed my whole house water filter for me as well. Friendly, helpful, caring service!

by Robert Rogers on Twintech Heating and Cooling

Very pleased with the professional service that TwinTech Heating and Cooling provided in replacing my furnace. I got several quotes from different service providers. Their price was excellent and they explained the features very well. We are very glad we went with TwinTech and highly recommend their services.

by Robert Mizuno on Twintech Heating and Cooling

We were new homeowners in need of a second opinion. TwinTech Heating & Cooling were Amazing and professional. Very knowledgeable and great service all around. Recommend to anyone looking for honest and reliable services. Treated with respect and care. Thank you Greg, Mitch and Bob!

by Ruth on Twintech Heating and Cooling

TwinTech is an excellent and honest company! I called them for a second opinion after being told by another company that I needed to replace my furnace. Turns out this was not the case at all! I did not need a new furnace. TwinTech did not push to make an unnecessary sale and saved me from a huge expense. Bob and Mitch were extremely professional and above all honest! I definitely recommend TwinTech!

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