Is it my thermostat or my furnace?

Author: Vivien Roberts  |  Last update: Monday, March 3, 2025

If you don't notice strange smells or loud noises from your furnace but it's not producing the right temperature, it's probably a thermostat-related issue. Additionally, if your unit's fan is running when it's off or the temperature changes on its own, it's also typically an issue with your thermostat.

How do I know if it's my thermostat or furnace?

Uneven Heating

Inconsistent heating patterns often point to thermostat inaccuracies, as the device struggles to regulate the temperature evenly. On the other hand if the entire house feels uniformly cold then the furnace might be the problem.

What are the symptoms of a bad thermostat?

What Are the Signs of a Bad or Broken Thermostat?
  • The AC or Furnace Won't Come On. ...
  • The HVAC System Won't Turn Off. ...
  • The Thermostat Is Unresponsive. ...
  • The HVAC System Short-Cycles. ...
  • The Room Temperature Doesn't Match the Thermostat Setting. ...
  • The Programmed Settings Reset Themselves. ...
  • Check and Adjust the Settings.

How do I tell if I need a new thermostat?

Signs You Need a New Thermostat
  1. Heating or cooling system will not turn off or on.
  2. The temperature reading is incorrect.
  3. Recent spike in your energy bill.
  4. Frequent temperature fluctuations.
  5. Thermostat is 10 years old or older.

Why is my furnace not running but the thermostat is on?

Possible reasons include thermostat issues (incorrect settings or dead batteries), power problems (tripped circuit breaker or blown fuse), and furnace malfunctions (dirty air filter, faulty ignition system, or tripped safety switches). Checking these areas can help identify the issue.

How to Tell if Your Home Thermostat is Bad - Bypass it and Find Out

How do I reset my furnace thermostat?

There is usually a small reset button somewhere on the thermostat. Finding this button may require that the thermostat panel be removed and pressing this button may require something like a paperclip to push. Hold the reset button down for 5 seconds and the thermostat should reset.

How do I force my furnace to start?

Checking your thermostat is the best place to start. Make sure it's set to “heat” and that you've set the temperature higher than the current room temperature. If that doesn't resolve the problem, try switching your fan to “on” to force the furnace to start working.

Can I replace my thermostat myself?

In most cases, installing a new thermostat is a relatively simple do-it-yourself project that can result in improved comfort and convenience and one that can help you save energy.

How do you know if your thermostat needs to be reset?

Common Thermostat Issues that Require a Reset
  1. Misreading Room Temperature: If your thermostat reads the wrong temperature, it won't kick the HVAC system on at the right times. ...
  2. Failure to Turn On HVAC System: A thermostat reset reboots its system and attempts to restart normal functioning.

How much does it cost to replace new thermostat?

The cost to install a thermostat is $182 on average, but you could pay between $113 and $264. Thermostats play an important role in our daily lives, cooling us down during the sweltering summer heat and keeping us warm and cozy during winter. While the average cost to install a thermostat is $182, pricing can vary.

How do you check if a thermostat is working?

Turn on the heat on the thermostat and increase the temperature. You should hear a sound from both the thermostat and the furnace, and whichever doesn't make a sound has a problem.

Why is my furnace not kicking in?

There are several reasons why your furnace may not turn on. The most common include a broken thermostat, gas line issues, clogged air filters, blocked ductwork, a tripped circuit breaker, and issues with the furnace itself.

What is the life expectancy of a thermostat?

The Lifespan of a Thermostat

On average, most thermostats last about 10 years, depending on the model, usage, and proper maintenance. However, many people decide to replace their unit sooner to take advantage of new energy-saving technologies.

Does the furnace control the thermostat?

Temperature Control

The temperature in a home is regulated by the thermostat installed on your living room wall. The thermostat can receive power from the control board in the furnace, or by its own batteries.

How do you know your furnace is going out?

If you put your hand to your home's heating registers and feel cold air blowing out instead of warm air, this is one of the signs your furnace is going out. Oftentimes, cold air coming from vents means that your furnace's blower fan isn't functioning correctly.

Why is my thermostat not turning the heat on?

If your thermostat won't turn on the heat in your home, change out the batteries and see if that fixes the problem. If not, your faulty thermostat could be the result of the following: A tripped breaker. Loose wiring.

How do you tell if you need a new thermostat?

7 Signs You Need to Replace Your Thermostat
  1. Your HVAC Keeps Turning On or Off. ...
  2. Faulty Thermostat Readings. ...
  3. Suspiciously High Energy Bills. ...
  4. Constant Temperature Shifts. ...
  5. Thermostat Is Too Old. ...
  6. Thermostat Fails to Respond to Changed Settings. ...
  7. Your HVAC System Short Cycles.

Where is the reset button on the thermostat?

Locating the Reset Button

Remove the thermostat cover by either snapping it off or unscrewing it, depending on the model. Most modern thermostats will have a clearly marked reset button inside the panel. It's usually small and recessed, so you might need a pointed object like a paperclip to press it.

What happens when the thermostat goes bad?

A malfunctioning thermostat will have trouble keeping your home's temperature at the right setting. If there's something wrong with the motherboard, it may change its own settings at random. You can test the thermostat by lowering the settings to see if the problem persists.

How expensive is it to move a thermostat?

Moving a Thermostat: If the required wiring exists at the desired location, moving a thermostat may cost as little as $65. However, moving the unit can entail installing new wiring and cutting and patching drywall, so the project can cost up to $450.

Can I just buy a new thermostat?

You can typically just replace the outdated thermostat with a new thermostat – assuming the latter is compatible with your HVAC system. There are a few things you should know, however, when upgrading your thermostat.

Why is my furnace not responding to the thermostat?

Check the Power Source Sometimes the problem between the thermostat and your furnace is as simple as replacing the batteries. Many digital thermostats use standard batteries to power their functions. Also make sure to check there is power at the furnace as well.

Where is the furnace reset button?

Typically, you'll find it inside the air handler, either next to or above your furnace. In most newer systems, the button is often directly next to the blower motor, while in older systems, it may be harder to spot as it is sometimes underneath or behind the motor.

Why is my heat not working but my AC is?

If your thermostat isn't set correctly, it can cause your HVAC system to blow cold air even in the winter. If your furnace filter is clogged, it can restrict airflow, causing the furnace to overheat and shut down the heating element. The blower stays on to cool down the furnace, leading to cold air circulating.

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