Is your AC unit running when turned off? If your answer is yes, there is a problem that needs to be solved. 

We composed this article; to help you solve this common problem of ‘AC won’t turn off at set temperature’.

First, we will help you understand why this happens. We start by answering the question why won’t my AC turn off. Then, we will tell you the specific reasons behind these problems. And most importantly, we will tell you how to solve this problem.

Let’s get straight into the details.

AC Unit Running when Turned Off: Understand your Thermostat

Does your air conditioner keep running for a few minutes when turned off? That is perfectly normal. The fans will keep running for a few minutes when you turn off your air conditioner.

However, if the fan runs for more than a couple of minutes, then you need to be suspicious. And, we assume that is why you are here; the air conditioner keeps running when turned off after, say after 10 minutes.

First, you need to know that the blower fan is a separate electrical system from the cooling system. They, however, work together as a system. As your air conditioner system cools down your house, the blower fan sucks in warm air from your indoors and runs it through the AC unit. It then blows the cool air back throughout your house.

When selecting “auto” as your thermostat setting, the blower fan and the cooling system should turn off simultaneously. This will happen automatically when the set temperature is achieved.

Keep in mind the blower fan will run a few minutes after your cooling system is turned off.

Remember that your blower fan will keep running continuously when you have “on” as your thermostat setting. Use the “on” setting to increase circulation in your house.

If you would love to change this setting, switch to “auto”.

Why Air Conditioner Keeps Running When Turned Off

Okay, it is time to look at why your air conditioner fan keeps running when turned off.

And on top of the reasons, we will tell you how you can solve that. You will know whether you need to call for AC emergency repair or if it is something that needs a quick DIY fix.

Let us get started on common reasons why your AC runs after being turned off.

Faulty Thermostat

If your thermostat is broken or damaged, your AC unit could stay in a continuous cycle. The thermostat controls the air conditioning unit. Therefore, if your AC won’t stop running, a faulty thermostat should be your top suspect.

If you have a damaged thermostat, you will need an HVAC professional to repair or replace your thermostat. Fixing or completing the replacement of a thermostat is not usually an expensive fix. However, it is something you want to do sooner before the damage gets out of hand.

Also, it would be ideal if you remembered that your thermostat gathers dirt over time. Accumulation of dirt interferes with the accurate temperature reading.

Important: We recommend replacing your thermostat after 10 years. If you have had it for more than 10 years, it could be the reason your AC unit won’t turn off.

Excessive heat

If there is a heatwave or the temperatures get over the roof in your area, it interferes with your air conditioning system.

A properly working thermostat will have a set temperature. If the set or desired temperature is not met, it will power your air conditioning system. If your air conditioner is constantly trying to keep up with high demand, it will have to run for a more extended period.

If there is a heatwave in your area, we recommend that you try to find other ways to cool your house. This is a way to support a stressed air conditioning unit.

You can support your air conditioning systems during a heatwave by:

• keep your house blinds open during the day, then shut them when the outdoor temperatures rise,
• invest in blackout curtains,

These can also help reduce your energy bills.

Wiring issues

A series of wires connect your thermostat, outdoor unit, and the entire AC system.

It is a common problem to have the wires disconnected or damaged.

If your air conditioner fan keeps running when turned off, the culprit could be wiring issues. Wiring issues need an HVAC technician. They will handle it well while eliminating the risks of electrical shocks.

Undersized Air Conditioner

A small air conditioner is another reason your AC keeps running when turned off. By undersized AC, we mean that the room is too big for the air conditioner.

If the AC unit is too small for the house, the system will be unable to cool the room temperature at an optimal rate. This means that the system may try to keep cooling the house when turned off.

The only solution to this is to get AC unit installation for an appropriate size system.

If you would love to receive enough cold air, you need to have the sizing right during AC installation. Getting an undersized or oversized system will come with regrets and wastage of money. 

Thermistor (Temperature Sensor) Issue

The thermistor collaborates with the thermostat to sense the room’s temperature. The thermistor is typically a tiny bulb close to the evaporator for window unit air conditioners.

The thermistor helps the thermostat decide when to turn the condenser unit on.

If you have a faulty, broken thermistor, that is the reason your window air conditioner keeps running when turned off.

You need to check whether the sensor is broken or disconnected. This involves your multimeter to check the relay board and other components of your air conditioner’s Electronic Control Board.

The Electronic Control Board (PCB Assembly)

A faulty electronic control board could be why your inside AC won’t turn off. The electronic control board is the control center of your AC unit. We like to perceive it as the brain of the AC unit.

The electronic control board receives and relays information to and from various parts of your AC parts. If the actual room temperature is too high, the thermostat notes this and relays the information to the electronic control board, turning the cooling system(compressor and fan) on.

If your AC compressor doesn’t turn off even after the ideal temperature has been achieved, your electronic control board or PCB is broken.

The only solution to this is getting a replacement.

A short circuit or a damaged relay

Another of the air conditioning problems that may result in an AC unit running when turned off is a short circuit.

The blower fan will keep running by itself when the relay switch is broken. This happens because there is no communication between the blower fan and the thermostat.

If you choose the on and off commands, they will not be sent to the blower fan if it is a short circuit. With this, the blower fan will keep running.

Your solution would be to call your local HVAC experts in this situation.

Faulty Fan Limit Switch

Even if you have the correct fan settings, the fan may continue running when the air conditioner system is not cycling. This happens if the fan switch is stuck on the override position.

You will need to reset the fan limit switch to get around this. The fan switch limit is located near the blower fan.

Dirty Condenser & Condenser Coils

How clean are your condenser and condenser coils?

Hot air moves over the indoor evaporator coil to cool your house, and heat is removed from the air. The refrigerant then moves through the lines, running out to the outdoor unit. The compressor pressurizes the refrigerant before having it transferred to the condenser coil.

Too much dirt, dust, and debris accumulate in this process on the condenser coil. This build-up of dirt limits the condenser coil from properly eliminating heat from the air. If the air condenser’s power is limited, it will have to keep running to cool the rooms in your house.

The solution for this is to check your condenser for any dirt. Look out for:

• bits of mulch,
• tall weeds,
• grass clippings

. These obstacles prevent air from flowing correctly. This makes the unit operate for longer in an attempt to desperately cool your house.

The trick for this is regular air conditioner maintenance and cleaning the condenser.

 Dirty Air Filters

Dirty air filters prevent proper air movement through the AC system. This will eventually cause several problems, such as running the AC unit after turning it off.

If you have a clogged air filter, the air conditioner keeps running more to try and cool your house. Therefore, if the fan keeps running after AC won’t stop running, you should ask yourself, “when was the last time I cleaned or changed my air filters?”

If it is more than a couple of months ago, you need to fix that. Change or clean your AC air filters at least monthly during your AC maintenance.

If you know how, you do not need to call your local HVAC Company to change your air filters. It is a simple DIY activity you can do on your own.

 Low Refrigerant Levels

Your AC unit runs perfectly on specific volumes of refrigerant to cool your house. If you have refrigerant leaks, damaged coils or damaged components that allow the refrigerant to leak from the system, you will soon have lower refrigerant amounts.

There will not be enough refrigerant to help your AC unit absorb heat if there are leaks. Therefore, the system has to run overtime to try and cool the house as needed.

Only your local HVAC company should handle issues involving refrigerants. Please send us a message or call at HVAC Santa Clarita to help get your refrigerant levels in check

Low Fan Speed

If the fan’s speed is low, there will be an inadequate amount of cold air reaching out to parts of your home. This generally results in poor airflow in the house.

Generally, dirt and grime stuck on your blower fan lowers your fan speed.

If this happens, your fan will try to run for longer to try and cool the living space more as needed. This is its attempt to increase the deviated airflow.

What to Do When Your Air Conditioner doesn’t Turn Off

First, you need to understand that your AC kicking on and off is different from it continuing running after a complete cycle. If your air conditioner keeps running after it is turned off, chances are you are having (1):

• an electrical problem,
• mechanical issues,
• or a technical problem.

If this happens, you will be worried and even start searching for “AC repair near me.” Which is a good move. However, by now, you are aware that there are simple issues you can solve on your own.

Yes, most of these problems are best solved by an HVAC professional.

However, here are some things you can do to help the situation before you can for professional repair.

If your AC keeps on running and does not shut off, try a few troubleshooting steps before calling a professional technician for repair services.

Adjust Thermostat Temperature Settings

The moment you find yourself in the “why won’t my AC turn off” situation, the first thing you should think about is your thermostat temperature settings.

Is the thermostat set lower than the current room temperature? If so, the cycle will not stop. Adjust your thermostat to several degrees higher than your room temperature if this is what you have. This will trigger the thermostat to shut down the air conditioner when the desired temperature is achieved.

Adjust Thermostat Fan Settings

First things first, ensure that your air conditioner is running, not just your fan. This situation makes it appear like the cooling cycle is continuous.

Start by checking the fan settings on your thermostat. Ensure that the toggle is in the “auto” position so that the fan runs only when the air conditioner is on. If the toggle is on “On”, move it to “auto”. And above all, ensure the set temperature is slightly higher than the current room temperature.

Eliminate Air Flow Restrictions

Another DIY ensures no obstacle preventing proper airflow through the system. Such obstacles are a huge reason your air conditioner stays on longer than it should.

In your regular AC Maintenance, ensure you eliminate airflow restrictions by:

• replace dirty air filters with clean air filters,
• clean any dirt accumulation g on the outdoor air condenser,
• keep room supply vents throughout the house open.

Clean the Blower Fan

A dirty blower fan is one of the top reasons for restricted airflow in the air conditioning system. If you have a dirty blower fan, it will run for longer to cool your house better.

You can remove grime from your blower fan using the following steps:

• switch off the electric power to the indoor AC unit
• Get off the access panel to the blower compartment
• Remove the screws holding together the circuit board in place. Ensure you keep all wires connected and move the circuit board away.
• Unscrew the screws holding together the blower motor assembly and keenly get it out of the cabinet.
• Use a soft brush to clean any grime and debris on the fan blades. You can vacuum debris from the cabinet and blades.
• Return the blower into position and fasten the screws.
• Reposition the blower assembly in the cabinet and secure it with a screw. Reposition the access panel.
• You can restore power to the unit.

AC Repair for Air Conditioning Unit that Keeps Running When Turned off

If your AC won’t turn off at set temperature and cannot figure out the issue, you are better off calling for a professional HVAC Professional.

Give us a call at HVAC Santa Clarita for regular AC repair or AC emergency repair. We will be glad to troubleshoot on the phone, come on-site, and professionally fix the problem behind an AC unit that won’t turn off.

AC Unit Running When Turned off FAQs

When your AC is off, but the fan is still running, the first thing you think about is searching for “home AC repair near me“. This is a good move that could put you in contact with local HVAC companies.

However, before that, you want to understand this problem well. We answer some frequently asked questions concerning an air conditioner that doesn’t turn off.

Why does the fan keep running when the AC is off?

If the AC fan is the only thing running after the AC turns off, there may be an issue with the relay switch. A faulty relay switch limits the communication between the fan and thermostat. This results in zombie air conditioners. Other issues could be wiring problems and short circuits. 

Why won’t my AC turn off? 

There are several reasons your AC won’t turn off. Top on the list is due to poor airflow and cooling process. In such a situation, the fan would run for longer to help cover up for the deficit. These problems often arise due to dirty air filters, dirty condensers, small air conditioners, or low refrigerant levels. 

What do I do if my AC won’t turn off?

The first thing you should do is to check your thermostat setting. If it is on “On”, switch it to “auto”. If this does not work, you can clean your air filters and condenser unit.

 If this does not yield the result, please give us a call at HVAC Santa Clarita. We will help you troubleshoot and repair your AC. 

 AC Unit Running When Turned Off Final Thoughts

When turned off, it’s time to call it a wrap for an AC unit running. If this is a problem you experience, you know the simple DIY tricks to get you around. Sometimes, this will have your system back on track. However, some technical and mechanical problems will need you to call for professional AC repair. 

If your inside AC won’t turn off, feel free to give us a call at HVAC Santa Clarita. We would be glad to offer your professional AC repair.

Source 

https://www.consumerreports.org/air-conditioners/troubleshooting-air-conditioner-problems-a5432764698/