Portable Air Conditioner Not Cooling – Causes + Fixes

When your portable air conditioner is running but not blowing cold air, it is a sign that something has gone wrong. Before working on a fix, troubleshoot first to find out the cause.

The reasons for a portable air conditioner not cooling include clogged air filters, low refrigerant (Freon) levels, faulty temperature sensors, or incorrect room sizing. To fix the portable AC, clean the air filters to remove any blockage, refill the refrigerant, and replace the faulty thermostat.

While some repairs are easy to do yourself, you might want to have a technician at hand to help fix the more technical problems such as a faulty thermostat and low Freon levels. Let’s dig deeper into the causes and fixes below.

Reasons Why Your Portable AC Would Not Be Cooling

Portable air conditioner not cooling

A portable AC unit can fail to cool a room for several reasons. The most common cause is refrigerant leakage, but clogged filters, a faulty thermostat, and too big a room are also possible issues you should troubleshoot.

Clogged air filter

Your portable AC traps dust and other particles in the air to keep your air clean for breathing. These particles are filtered using the air filters fitted on the unit. However, when there’s a buildup of debris and such dirt particles, the air filters get clogged, and the air conditioner will malfunction.

The portable air conditioner stops cooling effectively because of interrupted airflow. The fan may run when the unit is turned on, but there may be no free cool airflow in the room.

This happens if you stay too long without cleaning the air conditioner’s filters and drain systems.

Faulty thermostat sensor

A faulty temperature sensor can cause a portable AC unit to be erratic. The unit may blow off the air that’s not cold, or in some cases, the compressor will shut off unexpectedly and fail to cool the room.

If the AC cannot detect the room temperature correctly, it will not run correctly and therefore may blow out warm air when it should blow out cold air.

For example, a portable AC works by setting the desired temperature, and the unit will turn its compressor on and off to regulate the room temperature as required. If the temperature sensor is faulty, the unit will not cool the room despite these settings.

The best fix for this is to get a professional to replace the thermostat or temperature sensor on the unit. While you can do it yourself, it might not be a good idea unless you have the relevant skills to repair an AC unit.

Incorrect sizing

The size of an air conditioner refers to its cooling power, measured in British Thermal Units (BTU). If your portable air conditioner is not cooling the room enough, the problem may be incorrect sizing.

A portable AC placed in a room larger than its capacity to cool will not control the temperature correctly. For example, a 5000 BTU air conditioner should be placed in a 100-150 sq. ft. room. The AC will not cool the room effectively if the room is bigger.

The good news is that this is a problem you can quickly fix as there’s no mechanical fault with your AC. It is just a mismatch in BTU and room sizing.

Other common causes of portable AC failures include a dirty evaporator coil, too low fan RPM, loose or slipped fan motor belt, or a damaged compressor valve.

If you are in the market for a new portable AC, check out the IceHouse AC.

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Low Freon level

Some older portable ACs may contain a refrigerant gas – Freon – responsible for your air conditioner releasing cool air. If your older portable air conditioner is not cooling, the problem could be low Freon refrigerant.

  • Freon leakage can result in an AC unit running but not blowing cold air
  • Freon does not get used up; instead, it can only leak and get depleted.

A quick fix is to fix the leak and recharge the air conditioner. However, I wouldn’t recommend you do this yourself as this requires a specialist to ensure the right amount of Freon is refilled. Too much or too little Freon will still cause the air conditioner to malfunction.

PS: Freon is a brand name for an older type of refrigerant used in air conditioners and other refrigeration systems. Other newer brands of this coolant are common in AC units manufactured after 2003, but Freon is used as a generic name for all these refrigerants.

How do you know if your AC is low on Freon?

A quick way to troubleshoot if the AC is low on Freon is to look out for these signs:

  • A running AC that doesn’t cool the room
  • Higher electricity consumption than before
  • Bubbling or hissing noise from the cooling line
  • Ice buildup on the refrigerant line

How long does it take for your portable air conditioner to cool your home? Is it longer than it used to take? This is one of the major signs your air conditioner needs to be recharged with a new refrigerant.

How to Fix a Portable AC that’s Not Cooling

What to do if AC is running but not cooling?

How to Fix a Portable AC that’s Not Cooling

1. Clean the AC filters

Your portable AC collects dust, mold, lint, pet dander, and other particles on its filters. If you have an air conditioner with washable filters, an easy fix to make it start cooling again is to remove the filter from the frame, shake it thoroughly to get rid of any dust and debris, and then fix it.

If the filter is washable with water, rinse it with plenty of warm water with mild detergent. Place it in a cool place and allow it time for the excess water to drip off and dry before installing it back.

Cleaning is a fix that works if your portable AC has HEPA or carbon filters. For other ACs, replace the filter as per the manufacturer’s instructions.

Note: Cleaning your AC’s filters also helps reduce faults such as water collection tank filling up quickly, excessive power consumption, and cooling inefficiencies.

2. Match the AC’s BTU to room size

After troubleshooting and determining that the portable air conditioner is running and blowing cold air but not cooling the room, you’ll be sure there’s a mismatch in BTU-room size.

To fix the failure to cool, calculate the square footage of the room in which you’re using the portable AC and check the BTU sizing chart to determine whether the unit is overwhelmed. You can then use the AC in a smaller room and get a unit with a higher BTU rating to cool larger areas.

Here’s a quick chart to guide you on the correct room sizing of your portable AC unit.

Room sizeAC Capacity (BTU)
100 sq. ft.5,000 BTU
200 sq. ft.7,000 BTU
300 sq. ft.9,000 BTU
400 sq. ft.10,500 BTU
500 sq. ft.11,500 BTU
800 sq. ft.17,000 BTU
1000 sq. ft.21,000 BTU

Keep in mind that size in square footage is not the only factor determining the BTU rating to choose to ensure your room is cooled properly. Other factors include the amount of shade/sunlight, whether or not there’s a kitchen included, and the number of people who use the room.

3. Recharge the AC’s Freon

How to fix a portable air condioner not cooling

For most air conditioners, whether portable or window ACs, the refrigerant is meant to last throughout their lifetime. If it gets depleted, then there’s a leakage in the system.

To fix the cooling problem, repair the leakage first and then refill the refrigerant with the same type of Freon recommended by the manufacturer. Some have a portable air conditioner recharge kit that can be used for this purpose.

If you’re unsure what to do, a repair expert should help you with the recharge.

Here’s a video guide on how to repair and recharge Freon on a portable air conditioner:

4. Fix the temperature sensor

A broken thermostat means the AC will not detect temperature change and know when to turn on or off. This results in the unit making the home cooler or warmer than intended as it turns on and off erratically.

Before working on a repair, check to ensure the temperature sensor is broken or out of place. On most air conditioners, the thermostat is located near the evaporating coils, which measures the temperature and makes the air conditioner cool or warm the room accordingly.

If you cannot remove it yourself, get in touch with an HVAC and AC repair specialist in your area to help you remove and replace the thermostat.

Common AC Brands and their Fixes

AC Brand Not CoolingCommon fix
FrigidaireCheck the air filter to see if it is clogged, causing airflow problems. Clean and remove debris from the filter if it is washable. If this does not fix the cooling problem, replace the filter.
HaierClean air filters, recharge the coolant or replace the filters.
InsigniaFix the refrigerant leakage, replace filters, or clean them if washable.
WhirlpoolCheck the fan to see if it is running properly, clean air filters, refill Freon, or replace the unit.
AmanaCheck and fix clogged or constricted ductwork and filters, respectively. Recharge the refrigerant.

Before attempting any repairs on your AC unit, check to see if you have a limited or lifetime warranty. This is something you want to mention to your repair technician as well to prevent voiding your warranty.

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