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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, Whitby on Twintech Heating and Cooling

Reasonable price and the workmanship was prompt and timely and the employees were great to deal with.

by Nadia, Toronto on Twintech Heating and Cooling

The sales process was friendly, informative, and very consultative. They worked hard to earn our business by taking a careful look around our home to assess our needs, providing a lot of information about the product, and answering all our questions and finding the right solution for our home at a competitive price. They prepared us very well for what to expect on installation day, and the installation went very smoothly - no surprises, all very professional! They gave us a call after installation to ensure we were happy with the work. We're very happy that we chose to work with TwinTech to get our new furnace.

by Private User on Twintech Heating and Cooling

Twintech promptly responded to request for quotation. They were thorough and helpful in explaining options. The quote was very competitive. Installation of new furnace was very professionally completed. Excellent work.

by Rita, Scarborough on Twintech Heating and Cooling

When our old oil furnace finally broke down we decided it was time to finally convert to natural gas and finally install central air conditioning at the same time. Knowing it was going to be a significant investment for us, we wanted to make the right choice. Twintech came highly recommended by a friend and we were not disappointed. From the first contact with the salesperson, until the final touches on the installation, we were so pleased with their service. Everyone from the company was so friendly, efficient and a pleasure to deal with. Best of all, the cost was very competitive. We would certainly recommend Twintech to anyone requiring HVAC work in their home.

by Bob S, Pickering on Twintech Heating and Cooling

Mitch from Twintech came out for our annual furnace inspection. We found him to be friendly, conscientious & he left the work area clean. We were also very impressed with the thoroughness of the job he did. This is the 2nd job we’ve had Twintech do for us & have been very happy with the results for each. We highly recommend this company. Thank you, Mitch, Dave & Greg.

by Brent L on Twintech Heating and Cooling

Work was done on schedule, professionally, according to quote and with minimal inconvenience to building users. Very happy with the end result. The only area for improvement from my experience - need more timely quoting process.

by Karen on Twintech Heating and Cooling

The team was great! Very knowledgeable, professional and extremely helpful. A few days after install the unit didn’t seem to be working, user error, but within minutes of contacting them..on a Saturday.. a tech was on the phone troubleshooting with us. I highly recommend Twintech for your cooling or heating needs. They stand by their products and a pleasure to deal with.

by Rob on Twintech Heating and Cooling

During the hottest week in the summer our old A/C decided to call it quits. I called Twintech Heating & Cooling after receiving a referral from a family member; came highly rated for being an honest, family-run business, who appreciates their customers. Dave was able to accommodate my hectic schedule and book a late evening appointment to walk through the specifics. Greg and Mitch arrived exactly on time a few days later, were very polite and friendly, and within a couple of hours had a new unit up and running. I also received a follow-up call to ensure we were happy with the Amana.

by Linda Robinson on Twintech Heating and Cooling

They were on time and very professional. I'm so glad I decided to go with Twintech, thanks!

by Famcam1953 on Twintech Heating and Cooling

Timely and appreciated - this was during the hottest days this year when our Air and Furnace way.
Efficient. Professional. No BS or overselling. What was promised, was delivered at a cost-effective price point.
Down to earth.

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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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