HVAC Troubleshooting
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7 Signs of a Bad Thermostat
Your HVAC thermostat is the control center for your HVAC system. When a home thermostat is working right, thermostat sensors determine the temperature in your home and signal your heating and cooling system to warm up or cool down your home, based on your set temperature.
Whether you have a smart thermostat, programmable thermostat, or traditional non-programmable thermostat, eventually, it will be time for thermostat replacement. Learn how to tell if a thermostat is bad, who to call if your thermostat is not working, and how replacing a thermostat can help increase your energy efficiency and reduce your energy bills.
There are multiple signs of a faulty thermostat – some of which can be fixed. Some bad thermostat signs can indicate the thermostat has failed and needs to be replaced. If an old thermostat isn’t working, it may be for a different reason than a newer thermostat.
In addition, remember that some bad thermostat symptoms can be caused by other issues. Let’s look at some of the signs of potential trouble.
Sign #1: The thermostat screen is blank
Most newer thermostats have a digital screen that displays temperature and other information, based on whether it’s a traditional thermostat or a smart thermostat. Don’t panic if you see a blank screen. It may be a simple issue such as:
No power to the thermostat. This can be due to it needing new batteries, having loose or damaged thermostat wiring, a tripped circuit breaker, or a dead thermostat. Replace the batteries, check for visible signs of problems with the wiring, and check the circuit breaker box.
The thermostat is on the same breaker as the HVAC system components. Note: This is typically the same breaker as your indoor furnace or air handler, not the outdoor AC unit breaker. If the breaker is tripped, consult with an HVAC professional. A problem with the system could have caused the breaker to trip and turning it back on again without fixing the problem could cause damage to the system.
If new batteries don’t help and you don’t see any problems with the wiring or the circuit breaker, try resetting the thermostat. If that doesn’t work, it may be time to replace the thermostat.
Sign #2: The HVAC system doesn’t turn on
If your air conditioning system or heating system won’t turn on, the thermostat may be to blame. It could be faulty wiring or circuitry. This means the thermostat is not communicating with your HVAC system to tell it what to do. Call an HVAC professional for help.
Sign #3: The HVAC system runs nonstop
Conversely, if your AC unit or furnace runs nonstop, the thermostat may be to blame, and not extremely hot or cold outdoor temperatures. Try turning the thermostat off. If your air conditioner or furnace continues to run, your thermostat may have bad wiring or need to be recalibrated.
Consult with an HVAC company to see what the problem is. The good news is that changing out a thermostat is a relatively straightforward fix that can save you money on your energy bills.
Sign #4: The HVAC system is short-cycling
Short cycling is when your central heating and air system turns on and off, running for a very short time without reaching your desired temperature. A lot of things can cause short cycling, including a malfunctioning or bad thermostat. If it just started happening, a dirty air filter or your thermostat could be the culprit. Change the filter to see if that helps. If not, call an HVAC services company.
Sign #5: You have erratic temperature changes
A failing thermostat can cause fluctuating temperatures throughout your home. If you suddenly have hot or cold spots, the thermostat could be to blame. But so could many other HVAC issues. If your HVAC system is failing to maintain a comfortable level of heating, cooling, and dehumidification, consult with an HVAC professional for solutions.
Sign #6: The thermostat shows incorrect temperature readings
When the thermostat is working correctly, it should reflect the correct temperature. Incorrect temperature readings could reflect improper placement of the thermostat, a need for recalibration, a short-cycling issue, or another HVAC issue.
Sign #7: The thermostat forgets your programmed settings
If you have a programmable or smart thermostat that forgets your settings or if your Trane thermostat keeps reverting to another temperature setting, it may need recalibrating or a software update. It doesn’t necessarily mean that the thermostat is bad.
However, if your thermostat is on the older side, this could be a leading indicator that it is failing. Consult with your HVAC service provider about your options.
If your thermostat isn’t working and your house is getting cold or unbearably hot because the HVAC system isn’t running, you need to call an HVAC professional. Faulty thermostat symptoms may be linked to electrical problems or miscommunication between the thermostat and your HVAC system – meaning there could be more than one problem.
If you have a Trane thermostat, refer to our Trane thermostat manuals for additional information about when to call for service.
If you’ve tried all the troubleshooting and an HVAC professional confirms that your thermostat is dead, you need a new thermostat. Replacing a thermostat is a job best left to an HVAC technician due to the wiring and testing needed. You also need to ensure your replacement thermostat is compatible with your HVAC system.
For example, not all thermostats are heat pump thermostats. In addition, if you have a variable speed system, you need a thermostat that can work with 700+ fan speeds for the best efficiency and comfort. Don’t spend any money until you consult with an HVAC professional.
Get some tips on how to find the right thermostat for your home.
If your thermostat bit the dust, now is the time to upgrade to a smart thermostat for the biggest energy savings. Smart thermostats are programmable thermostats with extra features to help you optimize your home comfort while cutting your energy bills. In addition, they connect to the internet, which is why they’re also called WiFi thermostats.
Before you buy one online, learn about the advantages of Trane smart thermostats and Trane Diagnostics. It’s a monitoring service for your HVAC system where your dealer can spot small problems before they become big ones. You can set this up through the Trane Home App, which also lets you control your heating and cooling system from anywhere, anytime.
In addition, our smart thermostats have outstanding warranties. While the other guys have a warranty of 1-3 years, Trane smart thermostats come with a 10-year registered warranty (5 for the XR724) if thermostat installation is performed by a Trane dealer and you or your dealer register it within 60 days of installation. Even our base limited warranty is better - generally 5 years (1 year for the XR724).
Learn about Trane’s Best Thermostats. Then schedule a consultation to learn how a thermostat upgrade can save you money on heating and cooling costs.
Anne Fonda, Content Writer at Trane Technologies
A Content Writer with Trane Technologies, Anne Fonda researches topics and writes for Trane® and associated residential HVAC brands. She works in collaboration with Trane Technologies subject matter experts, offering easy-to-understand, informative content on complex topics. Her goal is to help consumers make informed decisions on the products and services they need.
She has written for HVAC and other service provider websites for over 16 years. Before transitioning to web content writing, Anne had a 14-year stint as an award-winning journalist. She graduated cum laude from the University of Missouri-Columbia School of Journalism. When she’s not working, Anne enjoys playing word games, reading, gardening, spending time with family, and visiting gardens and museums.
Expert review by Michael Morey, Smart Thermostat Product Manager
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