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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 Peter, Pickering on Twintech Heating and Cooling

On coldest night of the year our furnace quit. At 8:40 in the morning Greg arrived and gave us a diagnosis and a recommendation. By 2:30 we had a new furnace and were warm again. Great company. Great customer service. Good reasonable price.

Peter, Pickering

by New Furnace Installed on Twintech Heating and Cooling

Twin tech team was very efficient and prompt. They provided a quote within hours of request and got the job done on time. No disruption to home function. We would highly recommend this team. Job well done.

by John from Toronto on Twintech Heating and Cooling

Our furnace bit the dust, and Twintech came out to troubleshoot and diagnose the problem within a couple of hours. Mitch was super helpful, patient, and answered all of our questions. When we decided to get the furnace replaced, the crew was over first thing the next morning and did a fantastic job. Not only did they complete the job in a few hours, but they cleaned up and respected our house as they went, and answered all of our follow-up questions. I've used Twintech for our HVAC needs in the past and will continue to do so. I'd recommend them to anyone, and it feels good to support a local, family-owned business.

by Ryan k on Twintech Heating and Cooling

Dave and the Twintech team were fabulous from day 1 and helped us through the process to identifying a new furnace and AC unit. This was our first time through this process and Dave did a thorough job explaining all the components and was very patience answering all our questions. Dave provided great insights and fair pricing.

The Twintech team did an awesome installation. Very clean and efficient. I would highly recommended their service.

by Louise in Scarborough on Twintech Heating and Cooling

We had a new Amana furnace installed by Twintech and we were very pleased with the installation. It is nice to have a warm house again.

by Private User on Twintech Heating and Cooling

Excellent job. Excellent service. Competitive price. Its rare to find a company with the knowledge and professional results we have experienced with Twintech. The clean and neat installation with attention to detail and drop sheers to respect our property is a clear indication of Twintechs high level of integrity. The 1-1/2 gas line upgrade they did for our pool 3 years ago was awesome. Can't say enough. Thank-you Twintech.

by Private User on Twintech Heating and Cooling

Twitch did a great job with the installation of our new furnace. I really appreciated their honesty and I could trust what they were telling me. Another company tried to suggest significantly more work at a greater cost claiming it was necessary to meet current building code. Twintech is very fair. All staff I meet were friendly, polite and trustworthy. I would recommend Twitch for a furnace.

by Private User on Twintech Heating and Cooling

This is a professional team that's easy to deal with. I would strongly recommend them

by hj.taggart in OSHAWA on Twintech Heating and Cooling

Very professional firm from start to finish!
They removed the old oil tank and furnace. They installed air conditioning and a new propane furnace.
Professional installation, on time and no mess.
Very pleased with their work and would highly recommend the company. Our house is three stories so they spent the time to do all the calculations to make sure we would have great performance on each floor.
Thank you again!

by susieschoeppler in Oshawa on Twintech Heating and Cooling

Upon a routine yearly maintenance, it was discovered there was a leak in the heat exchanger and a I needed a new furnace. I know nothing about these things and was completely stressed out. The company I had the maintenance plan with quoted me a huge number to rent a furnace, I just wanted to cry. Then I spoke to Dave at Twintech. He was so knowledgeable and calming, provided me a fair quote and within a few days I had an amazing crew show up to my house and install my new energy efficient furnace! I have already recommended these wonderful people at Twintech to a good friend of mine. Thank you Twintech!!

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See What Our Customers Are Saying:

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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