AC Repair Mississauga

Common Furnace Thermostat Problems

common furnace thermostat problems

Do you ever feel like your thermostat is playing tricks on you? Does it turn the furnace off at strange times or make changes that leave you shivering in your living room? You may be dealing with a malfunctioning thermostat. Before panicking and shelling out money for professional repairs, it’s worth looking at what issues could be causing the problem.

In this blog post, we’ll cover some of the most common furnace thermostat problems and provide tips on troubleshooting them. That way, if you don’t need to call an HVAC technician, you can take care of the thermostat issue yourself!

Problem 1: Poor Temperature Regulation

Temperature regulation is how your thermostat maintains your home’s temperature at a set point. It is done via a heating, cooling, or HVAC system that regulates the temperature according to the programmed thermostat setting.

Poor temperature regulation can happen when the furnace or heating system runs more than it should, resulting in energy waste and higher electricity bills. It can also leave you feeling chilly in some rooms and too warm in others. Temperature regulation issues can result from both thermostat-specific and system-wide issues.

Possible causes

  • Thermostat placement: The location of your thermostat can play a significant role in your furnace’s temperature regulation, as it can be adversely affected by heat-generating and heat-dissipating sources like fireplaces, direct sunlight, and air vents. For instance, a thermostat placed too close to a sunny window may detect a higher temperature and shut off the furnace prematurely.
  • Clogged filters: Poor air circulation caused by clogged air filters can cause your furnace to overheat, resulting in poor temperature regulation. It can also make the heat distribution inconsistent.
  • Thermostat malfunction: A malfunctioning thermostat can lead to severe temperature regulation issues. A thermostat that cannot detect the indoor temperature correctly may continually run your furnace to maintain your set temperature.


The solution to poor temperature must start with thoroughly diagnosing the cause. Simply adjusting the thermostat settings won’t fix the problem. Here are some of the solutions:

  • Thermostat placement: You can avoid the interference of external sources by positioning the thermostat away from sources of cool or hot air. For example, a location that has reliable airflow is ideal for the thermostat.
  • Air filter replacement: Dirty air filters can lead to poor air circulation, make your furnace work harder, and cause temperature irregularities. Regular filter replacement is essential.
  • Thermostat repair or replacement: If you’ve tried other solutions and still experience poor temperature regulation, your thermostat may need repairs or replacement. Contact an HVAC technician to have it checked out.

Problem 2: Thermostat Display Issues

A blank thermostat display is a common issue that many homeowners face. It occurs when your thermostat display doesn’t show information like the current temperature or setting. A blank thermostat display can make adjusting the temperature challenging and lead to higher electricity bills. Several factors can cause a blank thermostat display, and fixing the problem requires identifying the underlying cause.

Potential reasons

  • Dead batteries: If your thermostat uses batteries, a dead battery could be responsible for a blank display.
  • Wiring problems: Wiring problems such as loose, disconnected, or damaged wiring can cause a blank thermostat display.
  • Tripped circuit breaker: A tripped circuit breaker can cause a blank thermostat display or shut off your entire HVAC system, rendering it useless.
  • Internal issue: A faulty component or malfunction on the internal circuit board can cause a blank display.


  • Replace batteries: If your thermostat uses batteries, replace them with fresh ones, and check if the display comes back on.
  • Check the wiring: Ensure all the wires are properly connected and free of corrosion, dirt, or other debris. If there’s a fault, reconnect the wires or hire a technician to fix it for you.
  • Check the circuit breaker: If you suspect the circuit breaker, turn it off and then turn it back on to see if the thermostat display comes back on.
  • Hire an HVAC technician: If none of the above solutions works, your thermostat may have an internal issue, such as a faulty component or circuit board. Contact an HVAC technician to diagnose and fix the problem.

Problem 3: Short Cycling

Short cycling is when your furnace turns on and off too often, causing inefficiencies and straining your HVAC system. It can lead to increased energy bills, reduced equipment lifespan, and decreased comfort levels in your home. Short cycling may occur for many reasons, but it should not be ignored, as it can lead to long-term HVAC problems.

Possible reasons

  • Oversized furnace: One of the primary causes of short cycling is a large furnace that heats an area too quickly, causing it to turn on and off frequently.
  • Clogged air filters: Clogged air filters can restrict airflow and cause your furnace to overheat, leading to short cycling.
  • Thermostat location: A thermostat in excessively hot or cold air, like the kitchen or direct sunlight, can cause your furnace to short cycle.
  • Malfunctioning thermostat: A faulty thermostat can detect the wrong temperature setting, resulting in your furnace turning on and off more often than it should.


  • Right furnace size: A furnace that’s too small for your house will struggle to heat it, while one that’s too large may lead to short cycling. Consult an HVAC expert to know the right size for your home.
  • Regular air filter replacement: Clean air filters allow for proper airflow and reduce the risk of short cycling. A regular air filter replacement schedule can help you avoid the problem.
  • Thermostat placement: Avoid placing thermostats in locations affected by cold or hot air drafts, direct sunlight, or a kitchen area to regulate temperatures.
  • Thermostat repair or replacement: If your thermostat is malfunctioning, get it repaired or replaced by an HVAC professional.


Furnace thermostats can have common issues that result in short cycling, blank display, and inconsistent temperatures. Identifying the underlying cause and taking preventive measures is essential to prevent long-term problems and keep your HVAC system functioning correctly. If you’re experiencing any common furnace thermostat problems, contact an HVAC professional for help. They will identify the source of the problem and recommend repair solutions to ensure reliable comfort levels in your home.