Why is My Portable AC Not Cooling?

Portable AC Not Cooling

A portable air conditioner that is not cooling can be a source of great disappointment – especially if you walk into your home, apartment or room and find it uncomfortably warm on a hot day. The unit might be defective and need the attention of a trained technician. It might be time to replace it with a new one. But there are also reasons why your portable AC might not be cooling that will not require professional help or the replacement of your current unit.

Portable AC Not Blowing Cold

That’s a commonly searched phrase along with portable AC not cooling – why isn’t the portable AC doing its job?

Here is a list of several portable air conditioner problems out to check before you reach for the phone.

Portable AC Power Problem

All room-sized portable AC’s operate on standard 115 volt electrical power. If the lights in your room work but the AC will not turn on, check to see if one of these issues is the problem:

  • ON/OFF switch in the OFF position. That’s a fun way to say that the unit is turned off. It can happen. We can forget to turn it on, kids or someone else can turn it off – either way, your portable AC won’t cool if it’s not turned on.
  • Cord not fully plugged in. This sounds like a simple thing, but children or pets can bump the cord loose, or it could have come disconnected over time by the weight of the cord itself. Check also for a very loose-fitting cord in an older, worn-out wall receptacle.
  • Circuit breaker in a power strip that the portable unit is plugged into. Power strips almost always have a built-in circuit breaker. These may or may not give any indication that they are tripped. If you are using one for your portable AC, go ahead and switch it off and back on to see if that is the problem.
  • Circuit breaker in the main power panel is tripped. This would be the circuit breaker for the wall receptacles in the room where the AC is plugged in. If it is tripped, it will be in a slightly different position than others in the same row. It might also have a red dot or a small window that indicates it is off. Push it firmly to the OFF position to reset it, then push it to the ON position.

Timer Issues with a Portable AC

Many portable AC models have a 24-hour timer that can be set to turn the unit off and on at predetermined times. Check to see if this is the reason that your unit is not cooling – the timer is programmed to turn on at a later time. If you are unfamiliar with how the timer can be deactivated, check your User’s Manual.

Water Tank Full or Unit Needs Draining

Some portable AC’s have a removable water tank that collects excess water that has been removed from the air. Others have internal cavities designed to hold up to about a quart of water. Most will shut the unit off so the water will not overflow and soak the flooring. They will usually also send an LED error code or have a small light on the control panel to indicate this situation. 

After you have emptied the tank or drained the unit according to the instructions, your portable should resume cooling. See the User’s Manual for how to do this. If you no longer have the manual, find the model number on a plate somewhere on the unit, and search online for the manual. Most are available on the manufacturer’s website. For example, this LG portable air conditioner page offers a link to the unit’s manual in .pdf form.

Portable AC Temperature Setting Too High

Like all air conditioners, portables have a means of setting the temperature to what you want your room to be. The unit will cool until its temperature sensor is satisfied, then stop cooling. If the temperature setting has been set too high, the unit may sit there all day without turning on. This is something to check if your portable AC is not cooling. 

Push the “down” button/arrow, lowering the set temperature, to see if the unit will turn on and start the cooling process. If the setting on the unit gets well below the temperature in the room and still doesn’t come on, then check these other reasons a portable AC isn’t cooling.

Temperature-Sensing Remote

Another possible reason closely related to the actual temperature setting is that your unit has a remote control with the temperature sensor inside. Whatever the temperature where remote is, that is what the portable will see as having met the temperature requirement. If the remote is in a cooler location than the room where the portable is, it may not be sensing the need to cool and will remain in standby.

An example of how this can happen is that someone might walk into another room with the remote for the portable in their hand. Reaching the other room – which might be cooled by a different AC unit or central air conditioning, the person sets the remote on a table, forgetting to take it back where the portable is. The remote will sense the temperature in the cooler room, and the portable will stop cooling.

Wrong Mode

If your portable air conditioner is not blowing cold, check the mode!

Room air conditioners are much more sophisticated than they were a decade ago. They do more – have more performance modes, so they are more versatile, and therefore useful in weather ranging from hot to cool and clammy.

Portable AC Models
Portable AC Models

In order for a portable air conditioner to cool, it must be set to the COOL mode. Most units also have a DRY and a FAN mode, but neither of these will cool the room. The DRY mode will pull heat and moisture from the air, but will return the heat to the room rather than sending it outdoors through the vent hose. If you’ve had a dehumidifier and felt heat coming out the back of it, you’ll know what we mean. The refrigerant absorbs heat from the room, makes the coil very cold, and moisture in the air condenses on it. The water is drained away, but the temperature of the space isn’t changed. Be sure to check to see that your AC is in the COOL mode, or in AUTO, if it has that mode. Either of these two modes will cause the unit to cool your room when the temperature sensor calls for it.

Wrong Size Portable AC for the Room

In this case, the situation is not that the portable AC will not run, but that it is running, but not cooling the room – at least not very well. All room air conditioners – both window units and portables – are designed to cool rooms up to a certain square-foot size. If an air conditioner is not large enough for the room or zone it is installed in, it will not do a good job cooling that room. Indeed, it may never be able to attain a satisfactory temperature.

Did you know? Here’s the truth about portable air conditioners: The largest of them will cool up to 450 square feet. That’s a room roughly 20×22 or 15×30. Not huge, in other words. If you’re trying to cool a zone significantly larger than that, your portable air conditioner isn’t going to keep up on really hot days.

Several factors should be considered when deciding on the size AC you need for a particular room:

  • The physical size of the room in square feet. Multiply the length of the room in feet by the width of the room in feet to get this number. Look on the box that the portable unit is packed in or in the Specifications of a portable AC to make sure it will cool a room of that size.
  • The amount and size of windows that get direct sunlight in the afternoon and evening. We all know how hot it gets on the side of a car where the sun is shining directly into the windows. The same is true with house or apartment windows. If this is your situation, you might need an AC that is one size larger than what you have determined you need by square footage alone.
  • High ceilings (over 9 feet) or normally having more than 3 or 4 people in the room at the same time will also add to the difficulty a portable AC will have to keep the room cool. You do not need to go up another size for these last factors alone, but they should be considered when choosing the right size portable AC for a room.

Pro Tip: Do not make the opposite mistake of buying an AC that is much too large for your room – even considering the extra factors beyond square footage. A unit that is way too large for the room will probably cool it so quickly that it will “short-cycle”. That means it will reach the desired temperature and shut off before it has a chance to remove enough moisture from the air. The result will be that you have a cold, clammy room. That’s not a good situation.

Dirty Air Filters

Portable air conditioners usually have one air filter; some models might have two. Their function is to catch dust, pet hair or other dirt or debris as they circulate air around your room. If these filters become clogged it will have a negative impact on the unit being able to perform its cooling operation. An air filter that is extremely clogged can even cause the AC to overheat and shut down. Always clean air filters on a regular basis or whenever a reminder light or code indicates that they are dirty. Consult your User’s Manual for the location and cleaning of your air filters.

Defective AC Unit

Hopefully it won’t come to this!

We list this potential issue last simply because one or more of the reasons listed above will usually be found to be why your portable AC is not cooling as you want it to. However, there is always the possibility that a mechanical part or an electrical component in your unit has failed. If you have checked all 8 of the above possible reasons and found that none of them is to blame, it’s time to contact a reputable and competent service technician.

When to Replace your Current Portable AC

When do you need to replace your portable AC?

If you have had the air conditioner for more than a few years, it may be time to retire it and shop for a newer model. When asked when to replace your portable AC, we recommend doing it if it has already been repaired and if it seems “tired,” that is, no longer able to keep up with the heat and humidity, probably due to losing refrigerant over the years or the compressor wearing out. Both of those issues signal the end of the unit’s usefulness.

Pro Tip to leave you with: Before buying your next room air conditioner, read our Portable AC vs Window AC Guide. You’ll find surprising differences. 

Both portable air conditioners and window air conditioners have their place. For pure cooling power, however, a window air conditioner beats a portable AC quite easily. Our Guide explains why.

Written by

Rene has worked 10 years in the HVAC field and now is the Senior Comfort Specialist for PICKHVAC. He holds an HVAC associate degree and EPA & R-410A Certifications.

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