15 reasons why the AC is running but not cooling (and how to fix it)

Its summer time and time to revive units back to life. However, it’s also the time most homeowners realize it isn’t cooling as much as before, and how to fix it. There can be several reasons for this but we’re going to help so you needn’t break into a sweat, literally! Here are the top 15 reasons why the AC is running but not cooling your home as efficiently as before.

Cute girl next to a portable air conditioner

Why is my air conditioner running but not cooling the house?

Most common reasons 
Filter needs cleaning Sunny spot Thermostat settings
Improper placement Refrigerant needs refilling Refrigerant Leaking
Dirty outside unit Problem in the Ducts Tripped circuit breaker
A faulty motor Too much ventilation Sensor problems
Fan problems Clutter near the outside unit A fuse is blown

Let’s run through the most common problems of a non-functioning air conditioner.

  1. Filter needs cleaning

Now here’s an important but very common problem. Here’s a likely scenario: it’s the first hot day after spring and you’ve turned your AC on for the first time after a couple of months. But tit is only blowing wafts of hot air. Most likely the filter is dirty from bits of dust accumulating over the winter and the clogged dirt is blocking proper airflow.

Luckily this is a problem that you can repair at home within an hour. Simply turn it off, and remove the filter. Now remove the top attachment of your vacuum and run it over the filter to remove the dust. Now head over to the bathtub and use a mild soap solution to wash your filter and scrub gently. Rinse and leave to dry. Reinstall once the filter is dried completely. You should notice the air flow is better and cooler.

If you want to skip this process entirely, you can go for disposable filters to save on time.

  1. Sunny spot

A window AC installation may seem easy but prove inefficient if the window is in a sunny spot. The direct sunlight can make it harder to cool your home in the long run. Chances are there is space around your window model that is letting hot air in or cold air out, making it difficult to bring down the inside temperature.

You can try finding a window in the shade and move your unit to fix this. However, if this isn’t possible a simple curtain or shade can be a temporary solution to avoid overheating the unit.

  1. Thermostat settings

If you find yours is running but not lowering the temperature, the first thing to do is check the thermostat settings. Sometimes the mode might be incorrectly set to ‘Heat’ and not ‘cool’.

If you are unable to change the mode, get your remote control or touch panel on the AC checked.

  1. Improper placement

You may be wondering why the hall isn’t cold despite installing a split model. This might be simply due to the improper placement of the unit in line of direct sunlight as mentioned above. The other reason could be that it is only powerful enough to cool a medium sized room and it would have to work twice as hard and take much longer to cool a large hall or living room. With frequent doors opening in such a room, the heat will get in and thus the room might not get cold as efficiently.

air conditioners outside

Consider getting a more powerful model for a larger room. For instance if the room is between 200-300 square feet, consider getting a 1.25-1.5 Ton AC. For rooms even larger, it’s essential you go for at least 1.5 ton.

  1. Refrigerant needs refilling

Refrigerant is actually the liquid enabling the cooling aspect of the unit. Sometimes this will need refilling and you will need to call a professional or learn how to refill it yourself. If you find that the refrigerant is low due to leakage in the pipes, you’ll need to fix the holes. Read the next point on how to deal with this.

  1. Refrigerant Leaking

This is a phenomenon common to old ‘units since the metal pipes can corrode over time from formaldehyde or formic acid. This will mean seeking professional help to replace the individual coils or the entire coil system. In some cases, experts resort to welding the individual leakage points. If you’re looking to do this yourself, check out these welding helmets.

Only after fixing of all the holes in the coils should refrigerant be added again. Refrigerant leakage can cause environmental damage and thus should be monitored periodically.

  1. Dirty outside unit

You’ll find an outdoor counterpart in both split and window models. This outside part contains a condenser whose job it is the turn the hot air to cold. Since it is placed outside, it is prone to dust, weeds and debris. You’ll need to get your cleaning tools out and get to work on cleaning the outside unit and its immediate surroundings. This can also be done with an experts help. If you’re looking for an outside electric socket to help you clean and keep up with general maintenance, you might want to check out these extension cords by length.

  1. Problem in the Ducts

In a central air conditioning model, ducts will need proper and timely maintenance since ducts distribute the cold air throughout your home. Noise in the ducts will also alert you to any leaky ducts or obstruction in their working that is reducing the overall efficiency. Pests or incorrect installation can also be the cause of obstructions in the ducts. Seek expert help or learn how to clean the ducts yourself.

air conditioning units

If you live in a neighborhood with frequent power outages but want a cool home all day long, you can check out the best watt generators.

  1. Tripped circuit breaker

If your air conditioner is not turning on at all, this may be due to the circuit breaker that has tripped due to overload on the electric circuit. In this case, reset the circuit breaker and consider getting an expert check the total load on the circuit and reduce the number of appliances on the circuit. Or you can learn more about single phase and three phase power in your own time. We also have extensive guides on cassette toilets, amp breakers, UV light sanitizers and 20,000 BTU air conditioners.

  1. A faulty motor

If you find it stopped working, a faulty motor in the outside component might be a possible cause. The motor functions to convert the hot air into cold and if the air is blowing hot through your ac, it might be time to check the motor.

A faulty motor will need repairing or complete replacement with a new one. If you’re doing the repair work yourself or reinstalling a new one, check out these amp wire resources.

  1. Too much ventilation

Evaporators take the existing humid air and convert it to cold air and circulating to the room. However, if the room is filled with windows and doors that aren’t properly shut, the humid stuff will continuously seep in and hamper the cooling process. It will be almost impossible to reach the desired room temperature if this problem is not addressed, no matter how powerful your model is.

Portable air conditioner

If it isn’t possible to completely shut off outside air, consider curtain, drapes or shades to limit the outside air and sunlight exposure.

  1. Sensor problems

The sensor located behind the touch panel measure the temperature of the air going in. If the sensor malfunctions, the room temperature could be assessed incorrectly and this might cause the cooling to be off. Keep in mind the sensor should never touch the coils and other components. Consider checking it’s placement for any signs of damage or dislocation.

  1. Fan problems

If you find the AC is not cooling and upon checking the outside, you find that the fan isn’t working, you should press the reset or overload button. If the fan still doesn’t work upon resetting, try to turn the fan clockwise. If the fan blades have no issues while turning, it’s the capacitor that needs changing. However, if the blades don’t move or move with resistance and noise, it’s the fan that needs replacing. Research good fan options for your unit or seek professional help.

Man repairing AC units

  1. Clutter

The outside part needs sufficient air to dehumidify and send through the indoor unit. The outdoor part needs to remain clutter free and should have no overhead structures or any objects or plants 4-5ft. below. If you’re still confused between feet and meters, check out this conversion chart.

The outdoor unit will not be placed in a store room or adjoining wall of an inside room. It can only be placed in the airy outdoors in an apartment balcony, porch, garden or backyard.

If it is not placed in any of these places and is rather indoors, consider relocation and reinstallation for better functioning capacity and cooling. If you want to trim the trees around the outside unit, consider this wood chipper resource.

  1. A fuse is blown

If you’ve tried all aspects of troubleshooting and still can’t find the problem, it might be time to check your indoor and outdoor unit for any signs of a blown fuse. If it isn’t turning on, check the electric panel and call a professional electrician to fix the problem.

Now that you’ve learn the several reasons and their solutions to fixing the cooling of your air conditioner, let’s take a look at all the ways you can avoid such problems in the future.

rooftop air conditioning units

Tips to maintain it at home

Maintenance tips
Clean the filter Clean the drain system Prepare it for the winter
Clean the evaporator Comb coil fins Professional maintenance
  • Clean the filter every month – Cleaning a clogged and dirty filter could can lower your energy consumption from anywhere between 5-15%. In a central air conditioning unit, you can find the filter located in the return ducts. In case you wish to do away with the hassle of cleaning the filter every month in the summer season, its best to switch to disposable filters.
  • Clean the evaporator and condenser coils – Dirt enveloping the evaporator will reduce its ability to absorb heat which is why it’s essential to dust them off with a dry cloth once in two months in the summer season. The outdoor condenser is more prone to debris and dust since it sits in the outdoors with possible foliage, leaves and dusty winds. The outdoor coil must also be checked and cleaned with a dry cloth once in two months in the summer.
  • Check the condensate drain system – Take a stiff wire to pass through the drain pipe occasionally to check for any signs of clogging. If the water isn’t draining properly this can be damage your unit or possible leak from the outdoor part and stain nearby items.
  • Comb coil fins – There are aluminum fins on the condenser and evaporator that can get bent over time. This causes reduction in air flow and thus slower cooling. To tackle this you can buy a “fin comb” which will bring the fins back to shape.
  • Preparing for winter – It’s essential that you take care in packing up your air conditioner unit when it’s no longer going to be in use for several months to come. Purchase a cover and use it to shield the condenser from dirt and debris. You can also remove it, pack and store it in your home. Make sure the storage space you choose is cool and dry, free of moisture and any pests.
  • Regular professional maintenance – You can also hire a professional to check and service it at the beginning and end of the summer season to make sure it’s working at its best. The professional will clean all the parts and check refrigerant levels and for any signs of leakage, broken fans or blown fuses. This may cost you some extra money but consider it an important investment in preserving it in the long run and save all the money of buying a new one too!

picture of an air conditioner

That’s all, folks! Keep up the maintenance to avoid any problems with your unit. Or go through our 15 reasons to spot the problem you might be facing if yours isn’t cooling as much as before.

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