This can happen because your system is set to ON instead of AUTO, and a simple switch on the thermostat can do the trick. Another reason this can happen is because there is a delay between turning off the air conditioner unit and the actual system shutting down.
The Short Answer Is: When your air conditioning system keeps running and never seems to shut off, the problem could be linked to a number of malfunctioning components – frozen evaporator coils, a clogged air filter, a bad electrical relay switch that needs to be replaced, the fan blowing constantly, dirty condenser ...
Then, when the air conditioning is off, the contactor prevents electricity from entering your AC unit. Over time, your contactor can collect dirt, attract insects, or get stuck in a certain position. As a result, it may stop working properly—which can force air out of your vents even when your AC is off.
Why is my AC still on after I turn it off? Your AC seems may be suffering from multiple problems, including a clogged air filter, frozen evaporator coils, or even a faulty thermostat.
A fan may continue to run even when the furnace thermostat is off for several reasons: Fan Limit Switch Setting: The fan limit switch controls the operation of the fan. If it's set to run continuously or if it's malfunctioning, the fan may continue to operate even when the heating system is off.
If only the fan is running when the AC isn't, there may be a faulty relay switch stopping the settings you enter on the thermostat from being communicated to the fan. It's also possible there is another wiring issue or short circuit preventing the on and off commands from going to your fan.
The thermostat is blank but the fan works, what does that mean? If the display is not working but the fan is on and your thermostat is in the “auto” position, this is because the display controls the heating and the AC but in the “auto” position, the fan can automatically come on and off.
This can happen because your system is set to ON instead of AUTO, and a simple switch on the thermostat can do the trick. Another reason this can happen is because there is a delay between turning off the air conditioner unit and the actual system shutting down.
Malfunctions affecting different system components can prevent the conditioner unit from shutting down as expected, such as a clogged air filter, a frozen evaporator coil, a faulty electrical relay switch, a dirty condenser coil, a constantly blowing fan, a bad thermostat, low refrigerant, and other HVAC system repair ...
A flame sensor can get dirty over time, especially if you run your system with a dirty air filter which can cause it to turn the burners off too soon. If the burners are turned off, your furnace will not have a heat source, and cold air will blow out of your vents.
It is standard for the furnace fan to run for a bit longer after a heating cycle. This purposeful design feature is intended to disperse leftover warm air and preserve even temperatures across the entire residence. As mentioned, this usually happens for around one to five minutes before shutting off completely.
The AC itself isn't detecting the temperature in your home, so it has to rely on the thermostat.
If your air conditioning system won't turn off, there are most likely malfunctioning mechanisms, such as a faulty thermostat or fan limit switch, frozen evaporator coils, electrical issues, or incorrect thermostat or fan speed settings.
When the coils freeze, they can't efficiently transfer heat, causing your air conditioner to run continuously. This can be due to low refrigerant levels, poor circulation, dirty coils, power issues at the outdoor unit, setting the AC unit temperature too low at night, or power issues at the condenser.
Most modern thermostats will have a clearly marked reset button inside the panel. It's usually small and recessed, so you might need a pointed object like a paperclip to press it. For those wondering specifically how to reset air conditioner thermostat models, the process is generally the same.
If your air conditioner will keep running no matter what repair you try, malfunctions or faulty components are to blame. You could have a dirty air filter, clogged condenser coils, frozen evaporator coils, a broken relay switch, or a bad thermostat, amongst other common air conditioner issues.
Broken Relay Switch or Short Circuit: If only the fan is running, there may be a broken relay switch preventing the settings you enter on the thermostat from being sent to the fan. Similarly, a short circuit or other wiring problem could be preventing the on/off commands from being sent to your fan.
One possibility is that the contactor relay switch may not be working correctly. This component controls how the electricity gets to the compressor. If it's malfunctioning, power and amperage may be impacted, and you may hear the buzzing sound. The easiest fix is usually to replace the contactor relay switch.
A power supply issue is one of the most common culprits behind a blank thermostat screen. Thermostats typically require a constant power supply through batteries or a wired connection. If your thermostat is battery-powered, the first step is to check if the batteries have run out.
The most obvious sign that you need to change your thermostat batteries is when the thermostat literally tells you the batteries are about to die! Most programmable models will now flash a low battery warning, usually about a month or two before the battery completely dies.
If your fan limit switch is set to AUTO but the fan continues to run without ever stopping, you'll need to call a professional. Two problems that could cause your fan to run without stopping include: A bad fan limit switch that needs to be replaced. Bad thermostat wiring.