You’re sitting at home with the AC thermostat set at a comfortable 72 degrees Fahrenheit in the middle of summer and, instead of shutting off when the temperature hits 72, the AC keeps going for hours, cooling the home further.
This can not only make your home uncomfortably cool. It wastes energy, increases monthly electricity bills, and may overwork your system.
What do you do?
Here are some reasons that your thermostat is not shutting off at the temperature you set and a few troubleshooting steps you can take to fix the issue…
WHY IS MY THERMOSTAT NOT SHUTTING OFF AT THE TEMPERATURE I SET?
The main reasons for a thermostat not shutting off at the temperature you set are human error (the wrong thermostat settings or poorly positioned thermostat), a faulty thermostat sensor, AC system issues such as a clogged air filter or faulty primary control, wiring problems or an old thermostat that is malfunctioning.
The problem may also be due to issues with the ductwork causing uneven temperature distribution throughout the home.
With some of these issues, a few tweaks or steps by the homeowner can return the AC system to optimal performance—but others require the expertise of an AC repair professional to troubleshoot and fix.
STAY COOL ALL YEAR ROUND WITH ONE WAY AIR…
The team at One Way Air installs, services, and repairs all types of air conditioning systems in Southwest Florida. Get in touch with us here for a quote or call 239-233-4356 in emergencies.
HOW A THERMOSTAT SHOULD FUNCTION
The thermostat is the “brain” of your air conditioning, communicating with the primary control system of the AC unit to determine when the cooling cycle should begin and end.
A properly functioning thermostat uses its sensor to shut off the cooling when the desired temperature has been reached, i.e., that specified in the thermostat controls.
In summer in Southwest Florida, this should usually be somewhere between 60- and 78-degrees Fahrenheit depending on the time of day/night and preferences.
Once the AC is off, the thermostat normally waits until the room temperature rises a degree or two again above the specified temperature before automatically switching on the AC unit to begin another cooling cycle. This process should repeat so that the room temperature remains within a fairly narrow range during normal operations.
COMMON REASONS FOR A THERMOSTAT NOT SHUTTING OFF
Let’s take a closer look at why the thermostat may not be shutting off the air conditioning system when the desired temperature is reached:
THERMOSTAT SETTINGS ISSUES
The most obvious starting point is to check that the thermostat settings are what you think they are. Sometimes, a switch gets nudged or settings get changed by accident.
Regardless of the type of thermostat you use, the settings should show the desired temperature for different times of day/night and an option of ON or AUTO for the AC fan. If the AC unit still operates after the desired temperature is reached, it may simply be that the AC fan is continuing to run (i.e., it is set to ON rather than AUTO mode).
THERMOSTAT DIFFERENTIALS & ROUNDING
Thermostats have a “differential” or “deadband” built into them, i.e., an amount below the set temperature (often around 2 degrees Fahrenheit) when the thermostat will keep the equipment running to prevent short cycling (constantly starting and stopping). The AC may not turn on until the same differential is reached above the specified temperature.
Also, bear in mind that thermostats use “rounding” of temperatures so what you see on the display might not be the precise temperature in the home. This is another reason why AC systems sometimes run for extended periods even after the thermostat tells you that the specified temperature has been reached.
FAULTY THERMOSTAT SENSOR
A faulty thermostat sensor will detect the wrong temperature in the room and therefore send incorrect messages to the AC’s primary control. This will cause the AC to run for longer or shorter than required to meet the necessary temperature.
HVAC SYSTEM ISSUES
If your thermostat is not shutting the AC off at the desired temperature, you should rule out any problems with the functioning of the central air conditioning system itself.
Certain common issues can cause a multitude of problems, especially dirty or clogged air filters, which restrict airflow and can lead to heating and cooling systems performing unpredictably.
Other potential problems that will need to be checked and, if necessary fixed, before your AC system returns to peak performance are malfunctioning components like the blower motor or compressor.
AC WIRING PROBLEMS
AC wiring problems are another common reason why a thermostat may not shut off the AC when it reaches the temperature you set.
The thermostat must “talk” to the AC system and instruct it when to turn on and off. Loose or damaged wiring may interrupt the signals or cause them to be erratic, so the system runs for longer than necessary.
A POORLY POSITIONED THERMOSTAT
During a professional AC installation, HVAC technicians will ensure that the thermostat is placed in the ideal location away from heat sources and drafts and, usually, somewhere near the center of the home where the walls are well insulated.
Sub-standard installations can lead to problems with false thermostat readings that disrupt the normal cooling cycles and affect home comfort.
THERMOSTAT AGE & MALFUNCTION
Thermostats, like any HVAC component, can suffer from age, wear and tear, and over-use. If your thermostat is low-quality, aged over 10 years or has been damaged, it may start to malfunction and cause inaccurate readings or erratic performance.
For the sake of a small investment, it’s often best to upgrade your thermostat if it is regularly experiencing age-related performance issues.
FAULTY PRIMARY CONTROL
Your air conditioner’s primary control unit is responsible for communicating with the thermostat. If this experiences a problem, communications may again be interrupted or erratic, leading to an AC that runs constantly or well after the desired temperature is reached.
LEAKING DUCTWORK
If air is leaking from ductwork, your entire AC system may struggle to reach the desired temperature, causing it to work harder and longer to cool your rooms.
This is not good for any aspect of your air conditioning—home comfort levels, energy bills, AC costs, repair bills, etc.
TROUBLESHOOTING YOUR THERMOSTAT PROBLEMS
The reasons outlined above for a thermostat not shutting off when the temperature is reached should help you check for problems if you suspect your thermostat of behaving erratically.
Here’s a quick checklist of troubleshooting steps that Florida homeowners can tick off before calling the AC professionals:
WHEN SHOULD YOU CALL A PROFESSIONAL?
Most homeowners are not equipped to check the wiring or troubleshoot more complex issues with air conditioning and thermostats.
You should call an AC professional if you experience persistent issues that the above simple troubleshooting steps don’t resolve.
Anything electrical, any signs of component damage or any possible issues with AC coolant should certainly be handled only by a certified HVAC professional. A licensed technician will go deeper with troubleshooting, assess any damage or performance issues, recommend fixes, and prevent problems from worsening. Make the call if you are in any doubt.
HOW TO PREVENT THERMOSTAT PROBLEMS
You can prevent thermostat problems—like most air conditioning issues—with regular AC maintenance. During this process, a licensed technician will check for all the tell-tale signs of AC performance issues, including the thermostat and other components.
Ideally, book an AC tune-up annually before the summer and also if you experience any of these signs of AC issues.
You should also periodically check thermostat settings and take note of any signs that the thermostat is not shutting off the AC when it should. Old, outdated thermostats should be replaced with new models, which can solve many related issues and prevent new ones from arising.
Ultimately, by regularly monitoring and servicing your AC, you should be able to prevent problems, saving money, energy, and disruption to home comfort.
FAQs
If you’re in Southwest Florida, talk to an AC professional about how to keep your family comfortable all year round. Contact One Way Air today.
