“Why Is My AC Blowing Hot Air?” Don in Vacaville Asks an HVAC Expert

Don in Vacaville has what we in the heating and cooling business call a nightmarish AC scenario. He writes:

“As I’m sure you’ve noticed lately, our Northern California weather has started to get hot again. I, for one, am always flabbergasted by how quickly this happens. It seems like one day it’s 40 degrees and the forecast says it might rain, and the next we’re back to clear skies an highs in the 90s.

I like the heat, although on the first 80-degree day of the year, I always fire up my air conditioner. It kicked on just like normal. I heard it make all the same sounds that it usually makes and I even felt a steady stream of air coming out of its vents.

The problem is, the air was HOT. I want to know, why is my AC blowing hot air? I have to admit that I didn’t have an annual check-up done yet, but I have been really diligent about changing the filters in my HVAC system like you’re always telling us to do. Can you help me figure out what’s up?” – Don from Vacaville, CA.

Yowzers, Don. It’s never good when you need technology to do one thing, and it goes and does the exact opposite. There are a handful of reasons why your AC might be blowing hot air. You’ve checked some items of your AC service and maintenance list but not others, so I can’t pinpoint exactly what the cause might be without more information. So, let’s talk about the most common reasons why air conditioning units tend to blow hot air—as well as the most efficient way to get your AC fixed so you aren’t left sweltering in your own home.

Why Is My AC Blowing Hot Air? The Most Common Causes

Our friend Don’s problem with an AC that’s blowing hot air is a relatively common one, which is why I’ve talked about why your air conditioner is blowing warm air in the past. Since it’s so common, I think it’s important to discuss the potential causes here again, though. Many homeowners experience this problem come spring, but there’s some real diversity in the reasons why.

Here are the top reasons why Don’s AC unit is likely blowing out hot air:

• The thermostat isn’t set properly: I know this sounds really obvious, but I think every homeowner has accidentally switched their thermostat to HEAT when what they wanted was COOL. 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 unit and the outside one, which work in tandem to cool your home. The outside unit sucks in hot air via its fan. Its compressor then cools the air and pumps it into your home through the evaporator, where it is then distributed through your ducts and out to you. If the fan of the outdoor unit 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 an HVAC pro. Electrical problems are nothing to mess with.

When to Call a Pro If Your AC Is Blowing Hot Air

Given the complexity of some of the fixes, even ones that sound DIY, I’d highly recommend calling your friendly neighborhood HVAC technician to come and take a look, especially if you suspect you may have a tripped circuit breaker or some other internal AC problem.

The problems listed below, though, merit an immediate call to a tech:

• Leaks or pools of liquid: If you notice liquid is, or recently has been, leaking near your HVAC unit, call an HVAC 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 that involves working with chemicals. Call a 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 check-ups which should include having a professional clean this component.
• A frozen AC unit: It is, surprisingly, possible for your air conditioner to be too cold and even, in extreme cases, have its evaporator coil turn 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 issue 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.

I hope that’s helpful for Don, as well as for the rest of you who’ve recently had the unpleasant surprise of an air conditioning unit that’s suddenly blowing out warm air when it’s already toasty warm in your home. This time of year, any hiccup with your AC warrants a call to an HVAC service team so you can get to the bottom of why your AC is giving you the cold shoulder ASAP.

I can’t say for sure, but I suspect Don may have been able to avoid his issue altogether by sticking to our annual AC preventative maintenance checklist, but he can’t go back in time. So, what I’d advise now is to simply give the pros here at Bell Brothers a call. We can have that AC unit blowing cold air like it’s supposed to in no time at all!

At Bell Brothers, our trained HVAC professionals would love to help you make your home more energy efficient by installing central air conditioning—or even new windows. Contact us today to schedule a free consultation.

Wondering how to finance a new AC unit this summer? HERO is a unique financing option that helps California homeowners afford energy efficient upgrades to their home. Contact Bell Brothers, a HERO-approved contractor, to learn more. Our local HVAC, plumbing, and window specialists will walk you through the entire process, from applications to installation.

Image courtesy AndreyPopov