How To Tell If Your Thermostat Is Broken

If you feel a chill inside your home this winter, you might have a problem with your furnace — or it just may be your thermostat. Your thermostat is what tells your furnace to turn on and regulates the indoor temperature. Oftentimes homeowners who fear they have a furnace on the fritz just need to fix their thermostat.

How To Tell If My Thermostat Is Not Working

Why is my thermostat not working? It’s a frustrating situation but often has simple answers. Before diving into examining the thermostat, make sure your furnace is functioning. Check your circuit breaker to make sure power to the furnace is on. There may also be a wall switch near the unit that needs to be engaged. Change the air filter if it’s been more than three months.

To see if the thermostat is communicating with the furnace, set the temperature five degrees higher than your normal temperature and see if the heat kicks on — that should help you determine whether the device is prompting the furnace to engage. Obviously, if the system is set to “cool” and you want heat, switch the setting.

Now, to tell if your thermostat is not working, go through a quick DIY checklist before calling a pro. Depending on what you observe, you may be able to troubleshoot your thermostat problem yourself.

First, familiarize yourself with some common signs of a possible thermostat problem:

A Difference Between the Device Setting and Actual Temperature

If you check your thermostat and are surprised by the temperature it’s showing (perhaps it feels way warmer or colder in your home then the thermostat portrays), that is a sign that your thermostat is facing issues. Improperly detecting or displaying the temperature means something in your thermostat is broken and needs to be fixed.

So if the air inside your home isn’t possibly equal to the temperature your thermostat is displaying, consult an HVAC professional to determine the cause of your thermostat issue.

Unit Shows “Cool” Setting Instead of “Heat” (or Vice Versa)

If you’ve ever turned your AC on to cool your home during a summer heatwave, then you may have noticed a “cool” setting showing up on your thermostat.

If, however, you set your unit to cool your home and the “heat” sign comes on (or vice versa, the cool setting turns on when you set it to heat), then clearly your thermostat is not working and requires some attention.

Flashing, Faded or Otherwise Irregular Digital Display

Usually, a thermostat isn’t likely a very large screen, but that doesn’t mean it should ever be difficult to read. If it is, that likely means your thermostat is not working.

The letters and numbers on your thermostat’s digital display should be clear and easy to read, never blurred, faded, or flashing in any irregular way. If something irregular is happening with your digital display, then something needs to be fixed within your thermostat since the thermostat is not working properly.

Dirt and Dust Buildup Apparent on or Inside the Device

While having to dust the top and outside of your thermostat is perfectly normal, there should never be a build-up of dirt on the inside of your thermostat or any kind of hard-to-remove debris on the exterior.

If you notice dirt and dust in unusual places, it could result in your thermostat not working properly. If this is the case, your thermostat may need to be cleaned. If that cleaning is necessary inside your thermostat, consider calling in a professional HVAC technician so you ensure the job is done well and your thermostat isn’t damaged as it’s interior is cleaned.

The Furnace Kicks on or off at Unexpected Times

You may notice that your HVAC unit turns on and off as it heats or cools your home. It does this to keep your home at the temperature you determined, which often entails some on-and-off switching.

However, if your furnace turns on in the middle of the summer when you’ve set your thermostat to cool your home, you may wonder what’s wrong with your furnace when you should be asking, “Why is my thermostat not working?”

Additionally, if the furnace turns off randomly and your HVAC unit starts blowing cold air in the summer, you’ll need to get your thermostat and HVAC system checked.

Indoor Temperature too Hot or too Cold

The thermostat is there to allow you to adjust the temperature to your own liking. If you turn it too cold or too hot, then obviously the indoor temperature is going to be uncomfortable.

However, if you set your thermostat to a comfortable temperature and yet for some reason, the temperature inside your home remains too hot or too cold, then it’s possible that your thermostat is not working.

How to Fix a Broken Thermostat

Check the Batteries

Some thermostat models have batteries that need to be changed periodically. Look for a flashing display or other indications that your unit needs fresh batteries.

Be gentle when removing the face or battery housing from your thermostat — don’t force it off!

Some units run on mercury or batteries that recharge off the system and a quick battery swap won’t solve your problem.

Examine the Interior

When you remove the face of the device, check to make sure no wires have become loose inside. Reattach loose wires, if needed.

Over time, your unit may also become dirty or dusty, which can impede its function. Use a small brush to gently remove any debris, or blow it out with compressed air.

If you have an old thermostat, you may need to replace it entirely. Consider purchasing a programmable thermostat to make sure your HVAC system runs at maximum efficiency.

Consider the Position

In order to function properly, your thermostat should be placed in a central location, away from other electronics and devices that generate heat.

If your thermostat doesn’t seem to activate your furnace appropriately or heat your interior thoroughly, you might have a positioning problem rather than a defect with the device. Move it yourself if you have some handyman ability and a better location in mind.

If you need the skills and advice to relocate it, call an HVAC pro.

Call an Expert Heating Professional

If you’re stuck wondering “Why my thermostat is not working” but none of your DIY efforts succeed in resolving the issue, you may need to schedule service and call a technician.

Getting a furnace inspection and an HVAC system check-up every year also helps to identify problems with your thermostat preemptively.

Your technician should examine the device as part of the expert-recommended annual service.

Need help? John C. Flood provides expert, timely, professional service to customers all over the Washington, D.C., Maryland and Northern Virginia region.

We even offering discounts on Ecobee Smart Thermostat installations!

If you need service to your thermostat or furnace, contact us at (703) 214-5611 today.

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