Why Your AC Is Blowing Warm Air—And How to Fix It

Imagine coming home from a long day of work during the summer, sweaty and tired after your commute, and then switching on your home’s air conditioner and being greeted by a big blast of… warm air. Obviously, something is very wrong with this picture. An air conditioner that blows warm air is the equivalent of a vacuum that spits out dirt, a washing machine that stains your clothes, or a microwave that flash freezes your dinner. Simply put, it’s doing the exact opposite of what you want it to do.

As a homeowner who enjoys being comfortable, you’ll want to figure out why this is happening—and how it can be fixed. There are a few different reasons that your AC will betray you like this, some of which are easier to solve than others. Being able to identify the potential causes will help you determine whether a DIY solution is a possibility, or whether you need to hop on the phone with your friendly HVAC repair tech to call in for backup ASAP.

Opposite day used to be a ton of fun in grade school. As a homeowner, though, you want your HVAC system to act like a responsible adult who does its job. Leave the hot air to your brother-in-law who knows everything about everything—except maybe why your AC is blowing warm air.

Reasons Why Your AC Might Be Blowing Warm Air

The trickiest part about an AC unit that has started to blow warm air is that there are many possible reasons why, some of which you can easily fix by yourself in a couple of seconds, others that will most certainly require calling a professional. What I generally recommend to homeowners is looking for signs of a potential DIY quick fix first.

Here are some common signs of easily fixable reasons why your AC unit is blowing out warm air:

• The thermostat isn’t set properly: I know this sounds really obvious, but I think every homeowner has accidentally switched their HVAC to HEAT when what they wanted was COOL a time or two. The first thing to do if your AC blows warm air is to make sure the thermostat is correctly set.
• The outside unit is obstructed: The two main components of your AC are the inside and outside units which work in tandem to cool your home. The outside unit sucks in hot air via its fan while its compressor cools the air and pumps it into your home through the evaporator. It is then distributed through your ducts and out to you. If the outdoor unit’s fan is entirely obstructed by debris, branches, or a fence you built to hide it, though, it might not be able to inhale, meaning the cooling process never takes place. This is another easy fix: clear the blockage.
• A tripped circuit breaker: Your AC unit runs on electricity and sometimes (especially during particularly hot stretches of the summer) it gets overloaded and trips a circuit breaker. Depending on which breaker, this can sometimes mean the outside unit we described above loses power and can’t cool the air, but the inside unit keeps pushing out the hot air that’s presently in your ducts. This is another easy fix: flip the circuit breaker. However, if it quickly gets tripped again, you’ll want to call a pro. Electrical problems are nothing to mess with.

How to Fix an AC Blowing Warm Air

We touched a little bit on some DIY ways to get your AC to go from blowing hot air to once again blowing cool air, but those are just the simple solutions. What I want to discuss now are the problems that may merit an immediate call to your friendly neighborhood HVAC technician.

• Leaks or pools of liquid: If you notice liquid is, or recently has been, leaking near your HVAC unit, I suggest calling a tech. This almost certainly means that your freon is low, that you have a refrigerant leak, or both. Leakage could also be a sign your AC compressor is bad, which, as it happens, is one potential cause for the unit blowing hot air. No matter the cause, this is a complex fix, one that involves working with chemicals. Call an HVAC professional.
• A dirty evaporator coil: This one is a little harder to spot. In fact, I’m not sure that a homeowner without extensive experience working with AC units will be able to identify it. Dirt is probably your AC’s single biggest enemy; if it builds up on your evaporator coil, the unit won’t be able to properly cool air. One great way to guard against this is sticking to a schedule of annual AC checkups which should include having a professional clean this component.
• A frozen AC unit: It is, surprisingly, possible for your AC to be too cold and even, in extreme cases, having an evaporator coil that turns into a solid block of ice. When this happens, the coil then blocks any cool air that would otherwise flow into your home and the motor just blows hot air out. This is generally caused by turning the thermostat to the highest setting and having the AC go from totally off to ice cold too quickly, but it could also be indicative of severe problems with your thermostat. You can identify this problem if your AC tends to start off blowing cold air but then frustratingly switches to warm after a short time. Call a professional AC tech to check this one out.

There’s no good way for your air conditioner to break, but having it suddenly start to blow hot air when you least expect it on a hot, summer day might be the worst. The majority of the problems we discussed above can be taken care of before the weather gets too hot by following an annual AC preventative maintenance checklist.  

If you stay faithful and get your yearly visit from an HVAC tech, he or she can spot potential problems in advance. That way you never have to come home, head for the thermostat, and wonder why your house is only getting hotter. That would be like drinking a cup of coffee that makes you sleepy—and no one wants that.

Your AC, obviously, is not supposed to be blowing hot air. Contact the trained HVAC pros at Bell Brothers to have it fixed today.

Image courtesy Unsplash user Michael Browning