Why Is My AC Blowing Warm Air?

July 28, 2017

Your AC could be blowing warm air for a lot of reasons. Think of warm air like a fever telling your body you’re sick: it’s a common symptom that tells you something’s not working correctly in your AC.

So, without us looking at your air conditioner, there’s really no way for us to know exactly what’s causing your AC to blow warm air.

That said, in this article we’ll share 6 common reasons your AC could be blowing warm air. The first 3 are issues you can diagnose and fix, and the last 3 you’ll need a professional to fix for you. Here are the problems at a glance:

Issues you can fix:

  1. Thermostat is set to HEAT
  2. Clogged outside unit
  3. Outside unit is not receiving power

Issues a professional needs to fix:

  1. Low refrigerant (refrigerant leak)
  2. Dirty evaporator coil
  3. Leaky or disconnected air ducts

Let’s go into more detail about each of these issues and how to solve them. If the problem looks like something a professional should handle or you aren't sure, don't hesitate to reach our to one of our expert HVAC techs today. 


Easy “warm air” issues you can troubleshoot

#1: Thermostat is set to HEAT

Thermostat Set To Cool Not Heat

We know it sounds silly, but check to make sure your thermostat is set to COOL and not HEAT. Sometimes kids (or adults) accidentally switch the thermostat to the wrong setting so warm air blows into your home instead of cold air.

#2: Clogged outside unit

A dirty outdoor condenser unit.

Your air conditioner has 2 components: the indoor air handler, and the outdoor condenser unit. The outside unit’s job is to disperse heat gathered from your home’s warm air and release it outside.

But if your outside unit is clogged from debris then it could decrease your AC’s performance which could cause warm air to blow into your home.

Solution: Clear your outside unit of debris. To do so, follow these steps:

  1. Turn off power to the condenser unit at the outdoor shutoff switch.
  2. Use a broom to sweep away any dirt, leaves, or debris from your outside unit. You may need to use a wet/dry vacuum to clear the debris you can’t remove by hand.
  3. Wash the outside unit with a hose sprayer on medium power.
  4. Trim any surrounding bushes so that they are at least 2–3 feet from the unit on all sides.

The bushes near this outdoor AC unit are too close and should be trimmed.

#3: Outside unit not receiving power

If your outside unit isn’t receiving electrical power, then it could cause your system to blow warm air instead of cold air.

Solution: Check for loss of power. There are 2 places an outside unit can lose power:

  • The circuit breaker: If your outside unit draws too much power, it could cause your circuit breaker to trip. Check to see if the breaker tripped, then reset it. If it trips again, call a professional for help.
  • The emergency shut-off switch: It’s usually located on your home’s exterior wall, close to the outside AC unit. Make sure it’s switched ON.

When to hire an AC professional for help

#1: Low refrigerant (refrigerant leak)

Refrigerant absorbs the heat from your indoor air and carries it to your outdoor unit to be released outside.

If you have low refrigerant (almost always caused by a leak in the refrigerant lines or coils), it could cause your AC to blow warm air.

Only certified professionals should handle refrigerant because it’s a dangerous substance that could cause serious health problems

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#2: Dirty evaporator coil

A new, clean evaporator coil.

Your AC’s evaporator coil (located in the inside unit) is filled with refrigerant that absorbs heat from your home’s air. Once that heat is absorbed, your AC pushes cool air back into your home.

However, if your evaporator coil is covered in dirt and grime, the refrigerant can’t absorb as much heat, which means you’ll feel warm air blowing into your home.

You’ll want to contact a HVAC professional to clean your evaporator coil for you since the coils are delicate and require special tools to clean.

#3: Leaky or disconnected air ducts

Ducts in an attic space.

Your ducts are located in hot, unconditioned spaces like attics, walls and basements. If your ducts are leaky or disconnected, then warm air from those hot spaces will enter into your home.

Duct leaks are very common. In fact, according to EnergyStar, a typical house loses 20–30% of the air that moves through the duct system to leaks or disconnected ducts.

You’ll need a professional to inspect your ductwork and fix any leaks since they’re located in hard-to-reach places and require special skills to fix.

Need a Florida professional to find and fix the problem?

Contact Red Cap Air to schedule an air conditioning repair. We’ll get your AC back on track so it properly cools your home again.


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