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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 Private User on Twintech Heating and Cooling

Great service and great people to deal with, from sales to installer. I highly recommend this company.

by GR from Oshawa on Twintech Heating and Cooling

Twintech replaced our aging furnace and air conditioner recently. I highly recommend this company. Their quote was competitive, they were on time and respectful of our home and extremely professional. From the salesman to the installers and the owner who followed up afterward to ensure we were satisfied, we are very pleased with the service. We are looking forward to working with this company for all of our HVAC needs for the years to come. Excellent workmanship and service!

by nathans in Scarborough on Twintech Heating and Cooling

We wanted to get our AC replaced as it was 22-years old and added to this our furnace was costing more and more to repair. So, we decided to get both the furnace and AC replaced.

After going through a few quotes and product reviews we decided to go with Twintech. The three-men crew arrived early in the morning, wasted no time and got to work right away. By 2:00 pm, they were all done. I’ve found their work to be top notch and they were completely professional. I had all my questions answered to my satisfaction both during the progress of their work and at end.

I have pleasure in recommending Twintech to anyone who is looking to get their furnace or Ac replaced

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Our air conditioner died On a Saturday and within hours Dave came out to take a look and discuss replacement/repair options.
The new air conditioner was installed on the Wednesday. The new unit was installed quickly. The installers were friendly and cleaned up afterwards.
We noticed a slight leak around the furnace that night and they came out the next day and fixed the issue. It has been working great and is quieter than our previous unit.
Very satisfied and would highly recommend TwinTech.

by Nancy in Toronto on Twintech Heating and Cooling

I contacted TwinTech to replace my 20-year old A/C. Dave, their service rep, promptly replied and was at my home within 2 hours. He was friendly and knowledgeable and didn't try to upgrade or oversell their A/C units but suggested the best fit for my small 1000 feet bungalow. Although this was during a heatwave and very busy, they were able to fit me in 2 days later. The TwinTech crew installed a 1.5 ton Ducane A/C unit that is now running smoothly while maintaining a constant cooling temperature. The crew were very courteous, professional and efficient and I will definitely recommend TwinTech to family and friends. I much appreciated your great service.
Nancy M., Oshawa

by Private User on Twintech Heating and Cooling

We had a great experience. The guys who installed our a/c did a nice job. Cleaned up.

by Private User on Twintech Heating and Cooling

excellent crew, fast and efficient! Would call them again when I need a new furnace.

by Private User on Twintech Heating and Cooling

Professional, courteous and efficient, don’t need to say more than that! Use them you will not regret it.

by Private User on Twintech Heating and Cooling

TwinTech was a pleasure to deal with from the estimate through installation. We replaced a 28 year old a/c unit with one recommended by TwinTech's sales representative Dave who took the time to go over the product with us and answer any questions. The warranty is for 10 years parts and labour and they will complete the registration for you. Installation was by Greg (owner) and Mitch and Spencer who were quick and efficient and left everything clean and tidy.

by Private User on Twintech Heating and Cooling

Very professional, from the sales consultation and inspection to the final installation. Met every expectations we had for the job. A local business with great client support. We highly recommend. Twintech is a blue chip! Thanks!

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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.

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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!

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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.

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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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