AC Keeps Running When Turned Off: 5 Causes and How to Fix Them

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The off button on your air conditioner is meant to shut down your unit, but if your air conditioner fan keeps running when turned off, you may have an issue on your hands. There could be a number of reasons why your air conditioner won't shut down: from a broken relay switch to zombie air conditioners. Here are the common causes:

Causes of Air Conditioner Fan Running when Turned Off

Reason #1: Broken Thermostat

A faulty thermostat might be the reason for your AC refusing to shut down, particularly if you have your air conditioner set to a timer. When the weather is too hot out and the set temperature on your control panel is low, then your air conditioner keeps running to reach the desired temperature, regardless of the timer.

If your thermostat is not reading the actual temperature inside the room, then the air conditioner keeps running to reach the desired temperature. There are a number of issues that may arise with your thermostat, and you can contact us, your local HVAC company, to diagnose and fix the problem for you!

Reason #2: Short Circuit or Faulty Relay Switch

The relay switch is what switches the voltage of your AC unit on and off, and communicates directly with the thermostat and the AC unit itself. A fault in the relay switches can cause failures in the shutdown of the air conditioner, and a broken relay board is often caused by a short circuit or damage to your electrical wiring.

Reason #3: Inconsistent Mini-split Settings

If you have a mini-split system, and some units keep running when turned off, then you may have inconsistent settings on your individual units. You may have set the temperature control or timer differently in each unit, or settings may have been altered in the main control panel.

You'll notice the cooling system continues to blow cold air as it runs, which indicates your air conditioning systems working properly, but on different settings per unit. You don't need to contact an HVAC technician, but you should keep all settings the same across different units.

Reason #4: Fan is Switched On

Check if you have the fan setting switched on in your unit. Your air conditioner keeps running when turned off because the fan is set to continuously run despite not blowing cool air. In this case, your air conditioning unit is registering that your fan motor should keep running even when the cooling system is shut down.

Reason #5: Miscommunication with Control Panel

Another possibility is a miscommunication between your control panel or remote that keeps your air conditioner continuously running even when turned off. The air conditioning system may not read the command properly, and will run continuously as it does not read an initiated shutdown procedure.

A window air conditioner would typically have an electronic control board that controls the thermositor, which regulates the cooled air in the room to reach the desired room temperature. If your AC system is on a timer or power-saving mode, miscommunications with the control panel may cause your AC to keep running even after the timer has stopped.

Troubleshooting Guide

Tip #1: Check Your Thermostat Setting

If you suspect the problem is with your thermostat, you can easily check your settings at the main control panel. Consider setting the temperature to a higher, but comfortable, level to ease the pressure on your AC unit, and switch the fan off when not in use. In multi-split systems, ensure the setting is the same across all units.

Tip #2: Schedule Your Unit for Regular Maintenance

Regular professional maintenance services are essential in the upkeep of your AC system, especially as our aircon servicing company can diagnose any issues with your unit before they become bigger problems. Schedule a deep cleaning and maintenance with us, and enjoy the cold air of your cooling system longer!

Tip #3: Regularly Clean Your Air Conditioner

Cleaning your air conditioner is one key way you can maintain its good condition. A dirty air filter can cause a plethora of problems from short cycling, to faulty parts so you need to clean this component regularly. You can also clean the outdoor unit with a hose, and wipe down the indoor unit with a damp cloth to keep these clean.

Tip #4: Check Your Electrical Connections

Short circuits can severely damage your air conditioner as time goes on, contributing to the wear and tear of your AC, as well as high energy bills. Have the short circuit fixed immediately to keep your AC running smoothly longer, and contact an electrician for any issues with your wiring. Do not attempt to fix the issue yourself!

When in doubt, call the professionals! Luce Aircon is your trusted partner in bringing you the best aircon servicing across various types, models, and brands in Singapore. We'll get to the bottom of the issue, and repair your AC unit to be as good as new.

Check out our article on why aircon turns on and off!
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