Furnace Not Responding to Thermostat – What to Do?

If you live in an area where the weather tends to be cool year round, a functional furnace comes in handy. However, you may have recently tried turning on your furnace using the thermostat only to find it unresponsive. To find the best way to fix this, we asked HVAC experts, and here's what they had to say. 

When your furnace isn't responding to the thermostat, there may be an issue with the heating system or the thermostat itself. Defective wiring, a blown breaker, a clogged furnace filter, a lack of electricity to the thermostat, incorrect settings, and obsolete software could be the culprit.

That being said, you'll want to keep reading. Further down this post, we have taken the time to explain in detail, all you need to know about handling a non-functioning thermostat.

Homeowner inspects dirty air filters on furnace, Furnace Not Responding to Thermostat - What to Do?

Reasons Your Furnace Is Not Responding to the Thermostat

 Here are some possible reasons your furnace doesn't respond to the thermostat. 

1. Issue With The Thermostat 

Person adjusting the home temperature on a smart thermostat

When your furnace isn't working, one of the first things to think about is that your signals aren't getting through to the device. This suggests that there might be an issue with the thermostat you're using.

Since some require batteries to function, the problem might be as simple as a power shortage. However, it might be something more serious, like the thermostat itself being defective, so it needs replacing.

Also, there are situations when the thermostat may simply be incorrectly set. Your heat may not be turning on if you put up the software and then forgot about it. Make sure your thermostat is set properly, with the heat setting selected rather than off or on chill.

Also, you must ensure the thermostat you have is suitable for your furnace to function effectively. It is best to use a thermostat whose capacity and capabilities match those of your heating system.

Likely, the thermostat and the unit won't communicate properly if you install the wrong thermostat for your setup. You might even witness a complete system failure. Before purchasing a new thermostat, ensure you do your homework and speak with experts.

2. Wrong Wiring 

Your thermostat's link to the heating and cooling system may eventually break due to loose wires, fraying wires, or old wiring.

Make sure all of your connections are secure while carefully inspecting your wiring. Also, try replacing any wires that you or an HVAC expert determine to be defective.

3. Blocked Air Filter

Senior man changing a dirty air filter in a HVAC Furnace

This is a typical issue with heaters and air conditioners in general. Your heater may very well have a blocked filter if you switch it on, but it doesn't blow or at least doesn't blow heated air.

This happens when the filter accumulates dust, decreasing circulation all through the system and perhaps resulting in the heater shutting off. You can fix this by making sure your air filter is clean and unobstructed in any way.

Now, because of the size of the home and the air conditioner, there are many types and sizes of air filters to choose from. 

It would be advisable to make sure that you have your system tested if the air filter was clogged. This is because the blocked air filter may have allowed the soot to enter the system. Check out these air filters on Amazon

4. Damaged Breaker

The heater may sometimes trip its circuit breaker, turning it off for whatever cause. Make sure you inspect and confirm the condition of all of your breakers.

What's more, your furnace ought to have a switch that you can flip to turn it off. This could be the source of the problem, as it might have turned off accidentally. 

5. Belt Issue

Your furnace could at times be operating normally, despite appearing to be broken because of a blower problem. High-pitched noises coming from your furnace are a sign that the blower is out of alignment.

The only real course of action is to hire a reputable heating repair company to examine and resolve the problem with your system. There are several causes for this problem, some of which are as simple as lubricating or having a stretched belt.

How to Fix Furnace Not Responding to Thermostat - What to Do?

A woman turns down the thermostat

Since we have addressed possible reasons your furnace isn't responding to the thermostat, here are ways you can fix the problem. 

1. Check if The Thermostat is On 

Begin with the obvious when troubleshooting a furnace. Is "heat" selected on your thermostat? If so, make sure your thermostat is set high enough to turn on the furnace. Remember that before the blower turns on, your furnace must heat up first.

2. Check For Low Batteries on the Thermostat

The batteries in your thermostat might be dead. On their display screen, many smart thermostats have a blinking "low battery" symbol. Install new batteries if you receive a "low battery" alert.

3. Check if Your Heater Power Switch is Off

If your thermostat is functioning. Check for the switch that is attached to the furnace's side. It might just be a wall-mounted light switch. A switch and a fuse are in some furnaces. Look to see whether it has burned and turned black. Replace it if needed, then turn the switch up.

4. Check The Panel Door

Modern furnaces are equipped with safety controls on their front panels, which prevent the furnace from engaging if the door isn't closed all the way. Verify the security of your panel door. If you're uncertain, see your owner's manual.

5. Are The Vents Blocked?

Your output vent and register may be closed or obstructed if the furnace is on, but the room is still cold. This is typical with floor-mounted heating ducts.

Verify that the vents are clear and unobstructed by carpets or furniture. You'll see vents frequently beneath windows, close to outside walls. Even long curtains have the potential to block airflow or reroute it in an undesirable manner.

If your vents are old you can also replace them with new ones or even upgrade to a smart vent. See this Flair smart vent on Amazon. 

What Would Cause A Furnace Not to Kick On?

First, make sure the air filter is clean if your furnace won't kick on. Dirty filters can stop the furnace from kicking on and reduce airflow. Other causes of why it won't start can include wrong thermostat settings, failing to switch on the gas line, and a broken pilot light.

How Do You Reset The Thermostat On a Furnace? 

Hand turning a home thermostat knob to set temperature on energy saving mode

To reset the thermostat on a furnace, follow these procedures

  • Switch off the gadget.
  • Pull the battery cover (you might need to pull the thermostat off the wall if it's on the back).
  • Remove the batteries, then put them back in for five seconds.
  • Take out the batteries and reinstall them, but this time, do it normally.
  • Activate the device.

Why Does My Thermostat Not Auto Work?


HVAC technician installing batteries in digital heating and cooling thermostat

It is possible that the battery of your thermostat is low, which will prevent the auto mode from turning on.

Configuration Setting

Also, there is the probability that auto mode is disabled on the device, assuming it is enabled.

Faulty Wiring

Trained HVAC technician checking troubleshooting a thermostat

The auto feature may not be working properly in the case of damaged or faulty wires as a result of the wrong positioning of the thermostat.

Data Issues

Corrupt data may affect the firmware of the thermostat, which in turn, can hinder you from using any of the features.

The Blower is Faulty

Though less likely, often the blower may be the issue and would refuse to turn on automatically due to overheating.

How Do You Check If a Thermostat Is Working?

  • When the furnace's electricity is turned off.
  • The wires must be unscrewed and taken out of their terminals.
  • Twist the two wires' bare ends together.
  • Restart the furnace's electric supply.
  • At each wire connection, inspect and tighten the terminal screws.

How Do You Know If a Thermostat Is Broken?

  • The heater or AC won't turn off, or neither will the AC.
  • The room temperature differs from the thermostat.
  • Short cycling of the thermostat.
  • The thermostat loses the memory of programmed settings.

How Do I Test My Old Home Thermostat?

  • Step 1: First, turn off the HVAC system. If your device has an on/off switch, you can achieve this by turning it to the off position.
  • Step 2: Remove the thermostat cover.
  • Step 3: Unplug the wires from the terminals.
  • Step 4: Restart the HVAC system.
  • Step 5: Check additional wires.

Do Furnace Thermostats Go Bad?

The normal lifespan of a thermostat for upkeep, repair, or replacement varies depending on the brand and quality. However, you can count on your thermostat to endure for at least 10 years.

Thermostats may start to break down after 10 years. Check out this durable Honeywell programmable thermostat on Amazon.

To Wrap Up

From this post, we see possible reasons why a thermostat cannot turn on a furnace and ways to solve this problem. With the information available to you, you can identify and fix any issues you may currently have, either with your furnace or thermostat. 

To read more about furnaces and thermostats, read these engaging articles: 

How to Reset Thermostat After Replacing Batteries

What Should Thermostat Be Set at in Fall

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