How to Fix a Portable Air Conditioner not Cooling

How to fix a portable air conditioner not cooling? In this article, we’re checking the 6 most common causes, how to test your portable AC for them, and how to repair each of the causes.

Quick answer: Place your portable AC in a room that suits its size. Insulate the hose and window kit using aluminum wrap and HVAC tape. Clean clogged air filters and the evaporator coil. Then, drain the water tank. Finally, make sure your portable air conditioner is set to cooling mode.

6 Causes & Fixes for your portable air conditioner not cooling

Sometimes portable air conditioners just won’t blow cold air. Here’s why:

Use portable AC in a suitable room

Portable ACs are when compared to regular AC units, relatively inefficient. Their cooling capacity is hardly enough for cooling medium-sized rooms. For large living room spaces, even though your portable air conditioner blows cold air, it could be that it’s not enough for cooling.

How to test: Turn on your portable AC and feel the air coming out. Is it cold? If yes, then your portable air conditioner is working. If you are not sure, you can test with a thermometer. The cold air coming out indicates that your portable AC works. The amount of cold air is, however, not enough to cool down your room notably.

How to fix: Either use the portable AC in a smaller room, or get a properly sized portable air conditioner for your room. For most living rooms, you need 14,000 BTUs of cooling capacity or more.

“As a general rule, an air conditioner needs 20 Btu for each square foot of living space.”

Insulate hose and window kit properly

If your portable AC is properly sized for the room it’s in, a lack of proper insulation could also be the reason for your AC not cooling.

The reason is how a portable air conditioner works and is set up. A portable AC works about the same as a regular AC unit. However, there are two important differences

  • Most portable air conditioners have only one hose to vent the hot air. This means it has to suck in the air from your room. This creates a negative pressure and causes warm air to enter your room.
  • The insulation of the hose and the window kit. The insulation of a portable air conditioner’s window setup is usually non-existent. With a portable AC, you usually get a cheaply made plastic hose and window kit. This causes heat to reenter your room.

How to test: Touch the hose of your portable AC when it’s running. Is it warm? If yes, this indicates that heat re-enters your room.

How to fix: Wrap your portable air conditioner’s hose with this insulating aluminum wrap (click here to view it on amazon). Make sure you seal most air gaps in the window kit setup. It’s usually not possible to seal everything perfectly because the generic kits are not properly sized for your windows. But do your best. You can also close any air gaps with duct tape or special HVAC tape.

Clean clogged air filters

Portable air conditioners can stop cooling if air filters are clogged. An AC needs proper airflow for evaporating the refrigerant and for distributing the cold air.

You always have to ensure your portable air conditioner’s air filters are clean and free of dust.

How to test: Open your portable AC and check the filters. If you don’t know how to open it, check your manual. But usually, you can open the back side of your unit with a few screws or handles.

How to fix: Dry-brush your portable AC’s air filters. I highly recommend not to use water for cleaning air filters because the combination of water and dust is a perfect breeding ground for bacteria which you shouldn’t blow into your room. Also, your portable air conditioner will smell like an old vacuum cleaner.

Clean greased evaporator coil

For proper cooling, similar to air filters, your portable AC’s evaporator coil needs to be clean.

The evaporator coil is the most important part for heat exchange in an AC. It absorbs the heat from the warm air in your room. Without it, the AC would not work.

Any dirt or dust on it decreases the coil’s efficiency.

“Keeping your evaporator coil clean and well-maintained is crucial to maintaining the efficiency of your system. Dirty coils can increase the energy use of your AC unit by up to 30 percent.”

Samm’s Heating and Air Conditioning

How to test: Open your AC and check the evaporator coil.

How to fix: Use this evaporator coil cleaner (click here to view it on amazon) to remove oil, grease, and dirt from your coils. You can use an old toothbrush to get rid of the dirt. But you can also use special evaporator coil cleaners.

Drain the water tank

Your portable AC extracts humidity from the air during the cooling process. This accumulates water in your portable AC’s water tank.

If your portable AC has built-in overflow protection, it could automatically shut off or stop the cooling.

How to test: Check the water level in your portable AC’s water tank.

How to fix: Drain the water.

Set your AC to cooling mode

Aside from cooling, there are usually two other operating modes in a portable AC: heating and fan mode.

In heating mode, the portable AC produces heat. In fan mode, it blows air without heating or cooling (just like a regular fan).

It could be that your portable AC is not set to cooling mode.

How to test: Usually there’s a button or a sign on the portable AC panel telling you the mode it’s running. If you are not sure, check the manual of your specific model.

How to fix: Just change the mode to cooling mode directly on the front panel or using a remote.

Your portable AC is still not cooling?

If you followed all the steps in this guide and your portable AC is still not cooling, the problem is likely something that’s harder to fix.

It could be an issue with the electronic circuitry or a leaking duct system inside the portable AC.

In this case, you should either hire a professional to take a look at it, or you can also just get a new portable AC.

Portable ACs are relatively affordable, so getting them fixed might not even be worth it.

Generally, I am always trying to fix broken devices, but when it’s not feasible, then it’s not feasible. Have a look at whether you can find out more about your issue in forums and videos.

In case you can fix it yourself, do it. Else, just get a new AC!


To fix your portable AC not blowing cold air, make sure that you follow all the steps in this guide.

They are all regular maintenance checks that you should do on a regular basis. This ensures durability and improves the efficiency of your portable AC.