$49 / month O.A.C Including Install
$49 / month O.A.C Including Install

Furnace is Turning Rapidly On and Off

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Furnace is Turning Rapidly On and Off

Posted On: December 18, 2024

Furnace is Turning Rapidly On and Off

When your furnace is turning on and off rapidly, a situation known as short cycling, it can cause inefficiencies, higher energy bills, and wear on your system. Several factors might be causing this issue, including:


1. Dirty Air Filter

  • A clogged air filter restricts airflow, causing the furnace to overheat and shut down as a safety precaution. The furnace will attempt to restart, repeating the cycle.
  • Solution: Replace or clean the air filter regularly (every 1-3 months depending on usage).

2. Thermostat Issues

  • A malfunctioning thermostat or poor placement (e.g., near heat sources or drafts) can cause inaccurate temperature readings, leading to frequent cycling.
  • Solution: Ensure the thermostat is functioning correctly and is located in an optimal spot away from direct sunlight, vents, or drafts. Replace the thermostat if necessary.

3. Oversized Furnace

  • An oversized furnace heats the space too quickly, causing it to cycle off prematurely. This can lead to uneven heating and energy inefficiency.
  • Solution: Consult a professional HVAC technician to evaluate your furnace size. If it's oversized, replacing it with a properly sized unit may be necessary.

4. Blocked or Closed Vents

  • Obstructed or closed vents can disrupt airflow, causing the furnace to overheat and cycle off.
  • Solution: Ensure all vents are open and free of obstructions like furniture, rugs, or curtains.

5. Faulty Flame Sensor

  • The flame sensor detects whether the furnace is burning fuel. If it’s dirty or malfunctioning, the furnace might shut off prematurely.
  • Solution: Clean the flame sensor gently or replace it if cleaning doesn’t solve the issue.

6. Blower Motor Problems

  • A malfunctioning blower motor may fail to distribute air properly, causing overheating and short cycling.
  • Solution: Have a professional inspect and repair or replace the blower motor if necessary.

7. High Limit Switch Malfunction

  • The high limit switch shuts off the furnace if it overheats. If this switch is faulty or constantly tripped, it can cause short cycling.
  • Solution: Consult an HVAC technician to inspect and replace the high limit switch if needed.

8. Improperly Set Furnace

  • If your furnace is running on too high a setting for the size of your space, it can cause rapid cycling.
  • Solution: Adjust the settings or consult a professional for recalibration.

When to Call a Professional

If these troubleshooting steps don’t resolve the issue, or if you suspect a mechanical or electrical fault, contact a licensed HVAC technician. Short cycling can lead to more severe damage over time if not addressed promptly.



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See What Our Customers Are Saying:

by DG Sellers on Twintech Heating and Cooling

Professionally done and took care to cover all entry floors to the house for the installers to remove the old furnace and install a new furnace.
I also made recommendations of the tankless water heater that we had installed and items to address. We did not know they also installed tankless water heaters.

by Bill, Pickering on Twintech Heating and Cooling

Price was not the cheapest nor the most expensive of my quotes. It's the quality of the installation that makes for a good AC system. The twins' knowledge & professionalism was evident in the small details:
Very clean work. Greg made sure that the refrigerant level & temperature were correct. They reinstall the insulation & vapor barrier around the wall. The outside electrical cords were secured to the wall. Proud to support this local company. Thank you.

by Taz on Twintech Heating and Cooling

Great team of guys came to do the work. Very professional. Arrived on time worked very efficiently and were very clean. They answered any questions we had without hesitation. The air conditioner works great and is so quiet. I highly recommend them and they don't try to up-sell anything right from the start.

by Jordan on Twintech Heating and Cooling

The service was prompt, professional and very courteous. Competitive price. Would highly recommend this company.

by David on Twintech Heating and Cooling

Excellent workmanship, and quick response. Would recommend Twintech to anyone.

by Todd Whyte on Twintech Heating and Cooling

My existing 15-yr old A/C went down on me during the first major heatwave of the season. Researched my options, as well as a few different installers, and decided on Twintech.

They gave me confidence right from the beginning. Extremely knowledgeable. Their communication was excellent - always responded to questions quickly. Given we were in a heatwave, they were fully booked. However, within days they were able to fit me in due to a cancellation. Upon learning that the Amana unit I was getting installed was on backorder, TwinTech went to bat for me with the manufacturer and was able to get me the next model up within a day, for the same price - Amazing!

As far as the installation was concerned, I couldn’t be more impressed. These guys were clearly very experienced and did a fantastic job. Very clean, polite, timely & informative. They even thoroughly sealed all the exposed gaps in my ductwork. I’ve had plenty of heating and cooling work done in the past and have never used the same contractor twice because I’ve never been very impressed. However, from now on, I’ll always be contacting Twintech first!

by Jordan Arnott, Courtice on Twintech Heating and Cooling

They were very friendly and took care of everything. The install looks great (and works great), they were very knowledgeable. Installed our a/c efficiently despite the difficult install location both inside and outside and they made it work.

by Lori Ellis on Twintech Heating and Cooling

Phenomenal service, so glad I found these guys a few years back after being "hosed" badly by 3 other companies. I've recommended them to so many, and they all are so thankful.

by Jonathan Rogoza on Twintech Heating and Cooling

This company is fantastic. Dave came out and gave me a very honest and reasonable quote, unlike a quote received from another company. I had a bunch of questions that were easily answered and when I had questions regarding heating/cooling a previously unheated room above the Garage, Dave arranged for Greg to come out for an assessment of this new space and gave me his recommendation along with his professional thoughts on all of my options.

These guys have been nothing but Professional, honest and helpful along the way. I can't recall the two other guys doing the install, but they were great as well. Good workmanship, everything was cleaned up and everything functions as promised. I could go on and on about my experience, but it's all positive so what more could you want?

Give them a call, see for yourself. If I had to buy another furnace/AC or heat pump, they'd be my first call.

by Private User on Twintech Heating and Cooling

I hired twin tech to convert my townhouse heating from electric to gas and install a furnace and a/c unit. I had talked with many other vendors, and received several quotes, but chose them, and very happy I did. Here are some of the reasons why:
1. They were realistic about the timeline for the work, when they could start and how long it would take. (They said upfront, it was their busy season and would need to get back to me in 3 weeks, which they did):
2. They had a quote with options for me. They were clear about the entertainment of what they would and would not do (they’d build duct work, id need another contractor to box in ductwork). This allowed me to plan as I was my own general contractor for my renovations).
3. They spoke to me in a language I understood, neither too technical nor too simple. They answered all my questions as I had them. Everyone is so lovely to work with, the sales team and the contractors who are worked in my home.
4. It’s been 4 m since the work was complete. They still answer my emails and my furnace is working very well!

I unabashedly recommend! Price, customer care and quality workmanship were all amazing!

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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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