If your air conditioner doesn’t shut off or if it cycles on and off nonstop, you run the risk of paying higher electricity bills. Even worse, you may need to pay for expensive repairs caused by wear and tear as the system has been working too hard.
Healthy air conditioning units start and stop the cooling cycle and fan automatically. If you notice that your fan blade or compressor is working continuously, you need to get these air conditioner mechanisms and components checked:
- Temperature Control
- Temperature Sensor
- Electronic Control Board or PCB Assembly
If your air conditioner doesn’t stop running, chances are you need to clean the air filter, evaporator coils, or condenser. It may also be caused by a faulty thermostat or fan and motor issues. Frozen evaporator coils and leaky air ducts are also common causes of air conditioning problems
In this article, we’ll discuss why air conditioners won’t stop running. To get a clearer picture of how the issue comes up, we’ll start by discussing how air conditioning systems work.
How does an air conditioning unit work?
Modern air conditioning units are composed of circuit boards, fans, and wires that work together to achieve an automated cooling process.
When your A/C won’t stop running, the problem usually lies with the cooling system or the fan.
The cooling system is responsible for temperature regulation. When you set your desired temperature, the cooling system takes heat away from the room by sucking warm air and blowing out cool air into the room.
In a healthy air conditioner, the cooling system and fan will cycle on and off simultaneously, usually after a 15 to 20-minute cycle. Cool temperatures should last two to three hours per cycle and less on hot and humid days.
If you notice that the fan keeps running even after the cooling system is off, you are advised to inspect your unit.
Air conditioning system running constantly: Main components to check
If your air conditioner doesn’t stop running, these are the three components that you need to check:
Electronic Control Board or PCB Assembly
The electronic control board is the control center of the unit. This means that it’s responsible for relaying and receiving commands to and from all the mechanisms of the AC.
When the thermostat is set to a certain temperature, the PCB assembly relays the information to the cooling system and fan. If both or either of the components doesn’t stop running, then the issue is most likely due to the electronic control board.
If your PCB assembly is broken, the only option is to replace it with a new one.
Temperature control or thermostats have two functions:
- Thermostats are responsible for noting the room temperature and relaying that information to the PCB.
- Smart thermostats are programmable, allowing users to automate the use of air conditioners.
One common reason why air conditioners run continuously even when turned off is because of rotary dial thermostats. This type of thermostat has dials that need to complete a circuit to turn on the compressor when the room temperature is higher than the programmed temperature.
If the dials are stuck, the cooling system will continue to run even if the set temperature is achieved.
If a thermostat is broken, it’s usually replaced with a new one.
The temperature control and the temperature sensor (thermistor) work hand-in-hand to determine the room temperature.
When the thermistor is broken, the condenser might run nonstop even if the system is turned off. You need to check if the sensor is either broken or disconnected.
Why does my air conditioner run continuously?
Clogged air filter
When the air filter is clogged and dirty, airflow will be restricted. When airflow is restricted in your AC, it cannot efficiently remove heat and humidity to cool the air to your desired temperature.
Replace your air filter monthly to help your AC work properly.
Restrictive air filter
Even if you regularly replace your air filters, the type of air filter you installed may be too restrictive. Specialized air filters protect your home against dust and allergen, but they can restrict airflow.
If you’re having problems with your AC, you may need a filter with a lower MERV value.
Dirty evaporator coils
Evaporator coils should be cleaned at least twice a year.
If you miss regular maintenance of your evaporator coils, dirt and grime can increase your AC utility bills by 30%. This is because your AC system will work harder for longer hours to reach your programmed temperature.
To clean the evaporator coil, you will need to loosen the access panels. Use compressed air or a brush to remove surface debris. There are commercial cleaners available for evaporator coils, but you can also use a solution of mild detergent and water.
There are cases wherein heavily-soiled evaporator coils require strong chemicals or heavy-duty cleaning techniques and equipment. The process can include cleaning with a pressure washer, steam cleaning, cutting and reattachment of refrigerant lines, or refilling the refrigerant lines.
For heavy-duty HVAC cleaning, it will be best to call an HVAC contractor.
Since the condenser is exposed to the outdoors, there’s a big chance that dirt and debris is blocking efficient airflow. Homeowners are recommended to hire an HVAC professional to clean the condenser since the process requires special equipment and solutions.
However, if you want to do it yourself, make sure to carefully remove debris with a hose before applying condenser cleaner. Use a soft brush or a sponge to wipe down the condenser cleaner. Use a water hose again to rinse off the remaining foam and sud.
Frozen evaporator coils
The evaporator coils are likely frozen if your unit runs continuously while blowing warm air from the vents.
In this case, you need to shut off the AC immediately to prevent further damage. A local HVAC professional can quickly resolve this issue.
As mentioned in the previous section, a faulty thermostat won’t be able to tell the system that the desired temperature was reached.
Check if the actual room temperature is lower than the programmed thermostat temperature. If the room is already cool and your AC is still running, chances are the thermostat is broken and needs to be replaced.
Fan blade or motor issues
If the motor isn’t blowing enough air or if the fan runs slowly, the AC won’t be able to suck in hot air and blow out cool air.
Lowering the fan speed or cleaning the fan blades usually solves this problem.
Leaky air ducts
Cool air escapes through patchy ductwork. This means that the HVAC system won’t cool the room properly, and the unit will keep running.
To fix the issue, make sure to seal leaks and holes in the ductwork.
Undersized air conditioner
If your air conditioner is too small, it will continue running until the room temperature lowers. This makes the system work unnecessarily hard and puts stress on the components.
You may need to invest in a larger or more powerful AC.
An HVAC professional can do a load calculation to figure out the right size AC for your household. Load calculation carefully considers the room size, layout, sun exposure, insulation, windows, and more.
Insufficient refrigerant charge
Low refrigerant levels in the cooling system will make your AC work harder.
If the AC has a low refrigerant charge, the unit likely has a leak that only an HVAC professional can fix. HVAC services will then restore refrigerant levels after fixing the leak.
Need help with your AC? Call our AC repair specialists.
If your air conditioner is constantly running, your electric bills will soar and your HVAC system will eventually wear down faster.
If you have this air conditioner problem, you need to check several components, including the electronic control board, thermostat, temperature sensor, air filters, evaporator coils, condensers, refrigerant levels, and air ducts.
This may be too complicated for most homeowners to fix on their own. Get in touch with our highly experienced technicians at Complete Comfort. We offer our heating and cooling services 24/7 in Central Indiana.
Rest assured that we arrive in fully-stocked vehicles, ready to identify your HVAC issues and address the repairs as fast as possible. You can trust that our highly trained technicians only use durable and field-tested equipment to make the repairs.
Our emergency AC repairs services require no after hour-fees, so make sure to give us a call if you experience:
- Issues with turning your AC on or off
- Freezing and leaking
- Inaccurate or malfunctioning thermostat
- Hot air or warm air from the AC
- Loud noises from the AC (grinding, banging, and screeching)
In case of irreparable damage, we also offer AC replacement and installation services.
To keep your HVAC system in top shape, we also offer AC preventive maintenance plans at an affordable price:
- Air conditioner
- Indoor air quality
Give Complete Comfort a call at (317) 535-5073 or book an appointment with us online.