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Thermostat not working? How to tell if your thermostat is broken

how to tell if a 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 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
  • Unit shows “cool” setting instead of “heat” (or vice versa)
  • Flashing, faded or otherwise irregular digital display
  • Dirt and dust buildup apparent on or inside the device
  • Furnace kicks on or off at unexpected times
  • Indoor temperature too hot or too cold

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.

thermostat not working check the batteries

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.

thermostat not working check placement living room

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

If none of your DIY efforts succeed in getting your thermostat to function properly, you may need to schedule service. 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. If you need service to your thermostat or furnace, contact us today.