Why is my air conditioner not cooling my house?

02/21/194 min read

Have you ever asked yourself, “Why is my air conditioner not cooling the house?” Does turning up your air conditioner seem to have little to no effect on the thermostat? That’s not cool at all. It’s a big problem on uncomfortably hot days.

You probably paid decent money for the air conditioning (AC) unit to take your heat and humidity worries away, so why is your air conditioner not cooling your house?

Here are a few ideas to help you troubleshoot why you’re not getting the best performance from your home cooling system. We’ll give you a list of possible small issues that you can fix yourself, and signs to look for that indicate it’s time to call in an AC professional to fix the problem.

Why Is My Air Conditioner Not Cooling My House?

Dirty air filters

First, let’s start with the small stuff. Your problem could be as simple as dirty air filters. If your air filters are clogged with dust and dirt, the air won’t be able to move through them easily. This can lead to a less effective heating, ventilation and air conditioning (HVAC) system and higher energy bills.

The rule of thumb is to replace your air filters every 90 days or so. If you have pets that shed or people with asthma or other allergies in your home, change your filters even more often. Pet hair can cause dust to build up faster, and people with allergies and asthma are more sensitive to dust particles.

You can replace dirty air filters yourself. If you can see that the filter has a layer of dust covering the filter material itself, you’ll know it’s time to replace it.

Blocked condenser unit

Another possibility is that the outside unit vent for your air conditioner is blocked or dirty. The part of your air conditioner that’s outside is known as the condenser unit. It’s where your air conditioner sends hot air it collects from inside your house.

Since you want to make it easy for the hot air to escape, make sure your condenser unit is clean and not blocked by anything.

Here are some simple steps for cleaning an AC condenser unit.

Turn off the power to the air conditioner, both from the breaker box inside your house and from the outside.
Remove the fan cage from the top of the unit using a screwdriver or wrench.
Remove dead leaves and other debris from inside the fan unit using your hands or a Shop-Vac.
Remove the outer covers and vacuum up any dirt you see with the brush attachments.
Gently spray the fins from the inside of the unit with a garden hose. Spray the outside of the unit to clean the coils. Don’t use a pressure washer as it can damage or bend the fins.
If the fins still look dirty, use a fin cleaning spray from your local hardware store
Gently straighten any bent fins using a butter knife.
Rake leaves away and remove any tall grass, shrubs, or other debris blocking the vents or around the coils.

Once you’ve followed these steps, put your unit back together, turn the power back on, and give it a test.

If your air conditioner is cooling your home better now, congrats! If not, the problem might need professional attention.

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When to Call an Air Conditioner Professional

Low refrigerant

One of the problems that could be causing your lackluster air conditioning performance is low refrigerant. This isn’t something you can take care of yourself, but you can look for signs.

Look for ice on the condenser unit system outside and listen for a hissing noise somewhere along the refrigerant line.

Frozen evaporator coils

Another problem is frozen evaporator coils on the inside unit. This can happen because of low refrigerant or because the outside condenser unit is blocked.

If you see that your evaporator coils are frozen, turn off the air conditioner and call a professional. Running the AC with frozen coils can cause more damage.4

Duct leaks

Another reason your air conditioning system isn’t cooling your house could be that an HVAC air duct is leaking.

Calling a professional to thoroughly inspect the ductwork will get much better results than searching for a duct leak yourself.

Broken condenser

This is one thing that you probably won’t be able to diagnose yourself. There might not be any obvious signs other than that you’re not getting the performance you want from your air conditioning and your thermostat reads a higher than comfortable temperature.