Why Your AC Won't Turn Off and How to Fix It

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It is frustrating when we encounter problems with our air conditioner. One of the common aircon issues is the unit refusing to turn on, but what does it mean when the air conditioner refuses to shut off instead?

Here are the 5 common reasons why your air conditioning unit won't turn off, and what you can do about them:

Reason Description Solution
Set Temperature Too Low The AC unit works to maintain low cooling temperatures, and may refuse to shut off to keep the room to the set temperature. Avoid setting the temperature too low; set temperature to a higher but comfortable level.
Faulty Fan Limit Switch Fan limit switch is set to override the thermostat instructions, causing the fan to continuously run even when shutdown is initiated. Regular aircon maintenance should prevent faulty parts.
Control Panel/Thermostat Issues Control panel cannot connect to the AC unit due to low batteries or other issues. Change batteries or power source of control panel, or replace unit if damaged beyond repair.
Dirty Coils and Filter Dust and debris can cause problems like poor airflow, frozen coils, etc., causing the AC to overwork. Clean air filter and exterior unit regularly.Have an HVAC technician do a deep clean of the AC unit every 6 months.
Inadequate System Size Unit cooling capacity is too weak for the size of the room, causing the AC to work overtime. Upgrade to a larger system with a larger cooling capacity.

5 Reasons Your AC Won't Turn Off

Reason #1 Set Temperature is Too Low

When the temperature on the thermostat is set too low, the air conditioner works overtime to provide cool air enough to get the current room temperature to the set temperature. The air conditioner won't shut off as it cannot keep the room at the set temperature, so the AC unit runs continuously. This is often the case with units that have automatic shutdown features.

Reason #2 Fan Limit Switch

The fan limit switch can override an initiated shut down, causing the blower fan to keep running even after the air conditioner has been instructed to shut down. If the fan limit switch is faulty, or has been set to override the fan settings, then your air conditioner will continue to run regardless of the instructions from the thermostat.

Reason #3 Control Panel has Low Batteries

Check if you can control any air conditioner function from the thermostat or remote control. If you can't adjust the fan setting, cooling cycle, or other electrical components, then you most likely have a faulty thermostat. Often, the control panel fails to deliver instructions to the air conditioner due to low batteries.

Reason #4 Dirty Condenser Coils and Filter

One of the most common reasons for AC system problems is dirt. A clogged air filter and dirty condenser coils can cause the entire system to malfunction, leading to problems ranging from abrupt shutdowns to overheating. These components are essential to any air conditioning system, and can also cause the AC unit to continue running despite shutdown initiation.

A dirty air filter can also cause poor airflow and frozen evaporator coils, which will disrupt the cooling cycles of your AC unit, and cause the HVAC system to blow warm air instead of cool air. The air conditioner won't shut off properly as it fails to get the room to the set temperature on the thermostat.

Reason #5 Small System Size

Sometimes, the issue is not with the air conditioner components, but with the size. Air conditioners have different cooling capacities, and using a unit with a small capacity to cool off a large room can cause the unit to malfunction, refusing to shut off as it has not adequately cooled the room. In this case, you may need to upgrade your model.

5 Tips to Prevent AC Shutdown Problems

Tip #1 Set Temperature to a Comfortable Level

Avoid setting the temperature too low as this will cause your air conditioner to work overtime. Adjust the temperature higher to a cool, but still comfortable level. If the air conditioner cannot cool your room enough for you to stay comfortable, consider upgrading to a more powerful unit.

Tip #2 Regular Maintenance

Regular cleaning and maintenance is key in keeping your AC unit in tip top shape. At Luce Aircon, we take pride in providing our customers with quality maintenance services that would keep your air conditioner running smoothly for years to come. Have one of our technicians check your AC unit for any issues or problems.

Tip #3 Change Remote/Thermostat Wiring or Batteries

If the issue is with the thermostat, change the batteries of the control panel or remote control. You may need to check your breaker box for any tripped circuit breakers if your thermostat is wired to an electrical power source. If fixing the power source does not solve the issue, you may need a replacement control panel.

Tip #4 Clean the Air Conditioner

An air conditioner should be cleaned at least twice a year, or once every six months. This is to remove all the dust and debris that could potentially cause problems for your unit later on. Our technicians are well experienced in cleaning different types of air conditioners across multiple brands, so you can be assured they get the job done right!

Cleaning your air conditioner on a regular basis can be done at home as well. Clean the air filter under running water, and brush it with some soap to get rid of the grime buildup. Hose down the outdoor condenser unit while the AC system is unplugged, and use a can of compressed air to clear the dust from the evaporator coils.

Tip #5 Upgrade Your Air Conditioner Size

If you notice your room isn't cooling efficiently, or your air conditioner is working harder than it should to cool your room, you're due for an aircon upgrade. Aircons are limited in their cooling capacity, and larger rooms require larger units to keep cool. Talk to one of our technicians in choosing the right size and specifications of AC units that would be suitable for your room size.

Got Aircon Problems?

For any aircon issues and problems, Luce Aircon is here to assist you. With decades of experience in air conditioner services, we provide our clients with top-quality services from aircon purchasing, all the way to maintaining your unit for years to come!

Check out our article about aircon fan not working

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