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Why Is My Air Conditioner Not Cooling?

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When turning down your thermostat, you expect your air conditioner to supply fresh, cold air at the push of a button. Like other mechanical systems, your AC unit relies on a series of interactions between parts to produce cool air.

If one of these parts doesn’t do its job, the air conditioner won’t work. Here are some common reasons why your air conditioner isn’t cooling your home.

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HVAC Installation

Installation costs for common air conditioning units range from $500–$2,500.

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HVAC Repair

Depending on the repair, the typical cost ranges from $100–$2,000.

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Furnace Installation

Installing an electric furnace will typically cost $1,600–$9,700.


5 Reasons an Air Conditioner Stops Cooling

1. The Thermostat Is Set Incorrectly

For the thermostat to be effective, you need to make sure that it’s on the correct setting. The thermostat should be set to “cool” and “auto,” not simply “on.” “Auto” runs the air conditioner and circulates cool air as needed, whereas “on” runs the air conditioner at all times, even when cool air is not being produced.

2. You Have a Dirty Air Filter

The filter in your air conditioner traps harmful and irritating contaminants like dust, pollen, and mold spores. Over time and without proper cleaning, air filters can become clogged and prevent air from properly passing through. Additionally, when clogged air filters trap cool air inside the unit, the evaporator coil is at risk of freezing, which could restrict air flow.

3. There Is a Refrigerant Leak

The air handler, the interior part of your air conditioner, is home to the evaporator coil that is responsible for cooling your home. Warm air from inside is absorbed through the evaporator coil and transforms into a gaseous state. The result of this heat absorption is cool, dry air that is then pushed throughout the house through the unit’s blower and air ducts.

To keep the process continuous, the compressor puts the gas refrigerant under intense pressure, releasing the excess heat outside and transforming the gaseous refrigerant back into a cool liquid with the help of the condenser. The evaporator coil can then create more cool air by starting the process over again.

When there’s a leak in the refrigerant line, some of the fluid is lost during its cyclical transformation process, resulting in an inadequate amount of cool air being produced.

4. The Evaporator Coil Is Dirty and Freezes

The evaporator coil contains the refrigerant that cools your home. The coil absorbs heat from inside your home, pushing cool air to the blower and transforming the refrigerant to a gaseous state. If your evaporator coil is too dirty, this can prevent the amount of heat it can absorb, causing the cold evaporator to freeze over and disrupt the cooling process.

A frozen evaporator coil can also freeze due to a refrigerant leak. When refrigerant levels drop, so does the temperature which can freeze the entire evaporator coil.

5. The Air Conditioner Compressor Isn’t Working Properly

Your compressor pumps refrigerant from the outdoor unit to the indoor unit. As the liquid refrigerant moves into your home, it enters the evaporator where it absorbs your home’s heat and produces the air flow felt from your vents.

Once the refrigerant fully vaporizes, it brings all the absorbed heat back to the compressor. From there, the excess heat is transferred outside and the refrigerant returns to a liquid with the help of the condenser, starting the process all over again.

If the compressor breaks down, the refrigerant can’t undergo its eventual cooling process, with the result being warm air pumped throughout your home.

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How to Maintain Your Air Conditioner

When it comes to AC repair and maintenance, there are a few tasks you can tackle on your own. Before performing any DIY air conditioner maintenance, ensure your unit is completely powered off. This can be done through the exterior shut-off box or your home’s breaker box.

Clean your outdoor unit

The central air conditioner unit you see outside of your home houses the condenser and compressor. After turning off the unit and removing the top cover, remove any noticeable debris lodged inside. We recommend using gloves when reaching inside of your unit to prevent cuts from sharp parts or objects. If you want a more thorough clean, you can wipe the fan located inside the unit with a damp cloth and spray the fins that surround the unit with a garden hose.

Clean the evaporator coil

The evaporator coil should be regularly cleaned using a soft brush and coil cleaner. This will help maintain evaporator coil efficiency and keep your unit operating smoothly.

To clean your evaporator coil, first ensure your unit is completely off. Then, locate your unit’s air handler, usually situated in a closet or attic. Remove the air handler’s access panel and spray no-rinse coil cleaner directly onto the evaporator coil. Use a nylon or paint brush to gently brush off debris before replacing the access panel.

Change the blower filter

When a filter is clogged, cool air can’t reach your home. To maintain cool, clean air throughout your home, change your blower filter at least twice a year.

Read More5 Essential Steps for Window AC Upkeep

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When to Call in a Professional HVAC Service

With a little time and effort, you can maintain your cooling system through regular cleaning and maintenance. However, when it comes to mechanical breakdowns and technical questions, maintenance is best left to the professionals. Here’s when you should call an HVAC technician:

  • If a specific air conditioner part breaks down—When the condenser fails or the evaporator coil freezes over, they need to be properly repaired by a professional.
  • For routine inspections—Your air conditioning system should receive inspections by an HVAC professional at least once a year. This will ensure your unit is working properly and help identify any problems or premature wear and tear.
  • When looking to purchase a new unit—If you’re looking to purchase a new AC system, have a professional come out to identify the best unit size for your home. Too small of a unit will constantly run and be overworked, while too large of a unit can be subject to premature wear and tear from the system consistently cycling on and off. Your home needs a proper-sized unit that runs for the correct amount of time to comfortably cool your home.

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