Why Is My Portable Air Conditioner Not Cooling

Why is My Portable Air Conditioner Not Cooling?

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With the summer months upon us, many people are turning to a portable AC unit for a break from the heat. After a day out in the sun, the relief of stepping into a cool air-conditioned room is immediate euphoria.

Unfortunately, things might not always go according to your plan. Many run into the problem where their portable AC is no longer cooling as it should. So, what do you do when your air conditioner stops conditioning? Why isn’t it cooling? Let’s find out.

Related article: Dehumidifier vs AC: Which Is Better?

Why is my portable air conditioner not cooling?

Troubleshooting the problem is the first step to take when your portable AC is not cooling. There are a number of possible reasons why your AC unit is not cooling, and many of them are quick, easy fixes. Here are a few simple, but still common reasons why portable ACs stop blowing cool air!

Portable AC Power Problem

This may sound obvious, but the first thing to do when your portable AC isn’t blowing cool air is to see if there is a power problem.

Quick Fix/Solution:

From a socket, metaphor for saving electrical energy

Examine the cord and circuit breaker to see if there are any issues.

You may also try plugging the AC unit into a different outlet to see if it works. If there appears to be nothing wrong externally, consult a trusted technician to take a look at your unit’s internal circuitry.

Low Freon Level

It is fairly common for portable ACs to stop cooling because they are low on freons or refrigerants. When your AC is low on freons, the hot air that enters the cooling chamber gets sent out again before it has cooled to its desired temperature.

While it can be difficult to know if your AC unit is low on refrigerant without consulting a technician, there are a few key signs to look out for:

  • Longer cooling cycles
  • Higher energy bills
  • Frost buildup on AC components

These signs usually indicate that your portable AC is low on freons.

Quick Fix/Solution:

Sometimes, an AC that isn’t cooling properly may require a freon recharge. The United States Environmental Protection Agency mandates that only certified professionals are allowed to recharge your portable AC’s freon.

The cost of recharging your AC freon will depend on the type of freon used, as well as the service provider. For instance, it will cost more to replace an AC unit that uses R-22 Freon because supplies are scarce.

In most cases, your AC unit’s freon will need recharging when there is a leak in the system. This leak will also need to be repaired to get your AC functioning normally.

Faulty Thermostat Sensor

Thermostat sensors play a crucial role in keeping your AC unit running properly. A faulty thermostat sensor will give an inaccurate reading to the control board, causing your AC to stop cooling your room before it reaches your desired temperature.

Quick Fix/Solution:

If the thermostat sensor in your portable AC is malfunctioning, you need to get it fixed.

Air Conditioning Technician and A part of preparing to install new air conditioner.

If you suspect that you have a faulty thermostat sensor, the first thing you will need to do is refer to your AC’s owner manual for more info. In most cases, you will need to enlist the help of a technician or repairman.

Because thermostat sensors are located near the evaporator coils of your AC unit, repairs will usually need to be conducted by a technician. Depending on the severity of the damage, the thermostat will either need to be fixed or replaced.

Wrong Size Portable AC for the Room

When your AC doesn’t seem capable of cooling your room properly, you might want to take a look to see if it’s the right size for your room.

Using an AC that’s too large for your room will cause it to turn on and off frequently in response to temperature fluctuations, even if it hasn’t been running for long enough. Consequently, your room may feel humid and warm, which can negatively affect your body.

Meanwhile, an AC that’s too small for your room will lack the ability to cool your room to its desired temperature. It will work hard for a long time, often to no avail.

Quick Fix/Solution:

Modern living room cooled with mobile air conditioner

If your AC’s BTU is too large or too small for your room, you need to get an appropriately sized portable AC.

How do you calculate the right BTU for your room size? Simply multiply the length and width of the room to get its square footage, then multiply that total by 20 BTU. In other words, every square foot of your room should be allocated about 20 BTU.

To make things quicker for you, here’s a list of AC sizes you’ll need for several common room sizes:

Area to be Cooled (Square Feet)Capacity Needed (BTU per Hour)
100 – 1505,000
150 – 2506,000
250 – 3007,000
300 – 3508,000
350 – 4009,000
400 – 45010,000
450 – 55012,000
550 – 70014,000

This calculation gives you an ideal BTU you should shoot for. Avoid going too far beyond this figure, as this will hurt your AC’s cooling efficiency!

Room Not Properly Sealed

Yet another obvious troubleshooting method is to see if your room has been properly sealed. Open doors and windows allow hot air from the surrounding areas to infiltrate your room while allowing coolants emitted by your AC unit to escape.

Quick Fix/Solution:

The best way to solve this problem is to seal your room completely. Even small gaps can drastically reduce your AC’s ability to effectively cool your room.

Some of the usual suspects include gaps between the door and the floor, windows that are left ajar, and tiny air vents. Sealing these tiny gaps can make a world of difference!

Dirty Air Filters

young male technician cleaning air conditioning system at home

Dirty or clogged air filters may be the reason why your AC is not blowing cool air. Your AC may be functioning normally, but a clogged filter will prevent coolants from escaping the portable AC and cooling your room.

For that reason, one of the first things you should do when your AC unit starts giving you problems is to locate its filter and see if it needs to be cleaned!

Quick Fix/Solution:

Clogged-up AC filters are one of the most common reasons for an AC unit that is not cooling. The best part is, that this is one of the easiest fixes on our list!

To clean your filter, simply remove the trapped dust with a brush or trusty vacuum. If your filter is washable, feel free to rinse it under running lukewarm water. Thereafter, all you need to do is leave it to dry and place it back into your portable AC. That’s it! You’re good to go.

When to Replace Your Current Portable AC

Sometimes, replacing your current portable AC can make more sense than attempting to repair it. When an AC unit is too old, breaks down frequently, or is no longer operating efficiently, replacing your AC unit can give you more bang for your buck.

Soleus Air PSH-09HP-01

If you’re in the market for a new portable AC, it is important to do your research and find one that is appropriate for your needs. Let’s take a look at a few signs that you’re better off replacing your AC unit:

Your AC Unit is More Than 10 Years Old

Generally, a well-maintained AC unit lasts approximately 10-15 years. If your AC unit is past the 10-year mark and in need of expensive repairs, it would make more economic sense to replace it.

This is especially the case when you consider the fact that AC units become less efficient with age and more prone to breakdowns. Newer AC models are also likely to come with technological advancements that make cooling more efficient.

You’re Paying More to Keep Your AC Running

Just because your AC unit is still blowing cool air, doesn’t mean that it’s working properly. A malfunctioning or inefficient AC unit can cause your energy bill to skyrocket even if your usage hasn’t increased. These issues become more likely as the age of your AC increases.

Replacing your AC unit also allows you to switch to more energy-efficient units, allowing you to save on your energy bills over the long term.

Your Portable AC Uses R-22 Freon

master of repair air conditioners at work

As of January 2020, the US no longer produces R-22 Freon as a coolant due to its association with environmental damage. The R410A refrigerant is being used as a more eco-friendly alternative, and will eventually become the default.

This means that if your portable AC uses R-22, it will become harder and more expensive to maintain over time as the technology becomes obsolete. In short, if your R-22 AC unit is giving you trouble, you may want to seriously consider a replacement.

Common Brands and their Fixes

You can choose any AC brand that suits you. But we’ve gathered common brand faults and their fixes to make it easier for you to decide.

Soleus Air

Soleus Air 12,000 BTU Portable Air Conditioners 3-in-1, Air Conditioner

Soleus Air units (from Amazon) are typically easy to troubleshoot and fix if they fail to cool your room efficiently. The company recommends performing a few preliminary checks before consulting a technician.

First of all, you should check if the inlet or outlet is blocked. Then, check to see if your AC’s fan speed is set to low – if this is the case, set it to high. They also recommend checking to see if the filters are clogged, and if all heat sources have been removed from the room.

In some cases, your AC unit might display error messages, which will help with troubleshooting. A list of common error messages can be found below.

  • FAULT E2: The AC unit is too small for your room
  • FAULT E3: There is a coil-related issue, and a technician should be consulted
  • FAULT E4: Frost has built up internally
  • FAULT E5: General error message for a malfunctioning unit. You will need to consult a technician for a proper fix.


Whynter ARC-14S 14,000 BTU Dual Hose Portable Air Conditioner with Dehumidifier and Fan

Whynter’s troubleshooting guide covers many of the fixes listed above, with a few Whynter AC specific tips.

First of all, you should press and hold the MODE button until COOL is displayed. After doing so, wait 3 minutes for the compressor to turn on. If you notice a flashing red light with an error message STOP or P1, this means that the internal reservoir is full and should be emptied.

Under some circumstances, the STOP or P1 message may continue to flash after you’ve emptied the water reservoir. This usually indicates that there is a loose internal connection, in which case you need to contact a technician.


Emerson Quiet Kool 8,000 BTU Smart Portable Air Conditioner

Emerson recommends checking the filters and condenser coils as the first thing to do when your portable AC is no longer working. The other common issues have to do with the internal components of the portable AC. These components include:

  • Compressor
  • Thermostat
  • Control board
  • Thermistor
  • Run capacitor

Testing and identifying faulty internal components is a challenging task and one that is best left to the professionals. This will ensure that you don’t replace parts unnecessarily, or spend too much money on costly repairs.


If you find yourself with a portable AC unit that is not cooling, it is worth your while to do some troubleshooting before contacting a technician. In most cases, the fixes are relatively simple and can be performed without enlisting the help of a technician

However, portable AC units can malfunction because of an issue with their internal circuitry. These situations call for professional expertise.

We hope this article covered the key factors that impair AC cooling efficiency! Don’t forget to share this guide with a friend if you found it helpful!

Last update on 2024-05-24 / Affiliate links / Images from Amazon Product Advertising API

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