Why Is My Air Conditioner Blowing Hot Air? [How to Fix]

So why is your air conditioning blowing warm air when you have it set to cool?

Incorrectly set thermostats, refrigerant leaks, and clogged evaporator coils are all reasons that may lead to your air conditioner blowing hot air.

Below you’ll find out everything you’ll need to troubleshoot and fix your air conditioner blowing hot air.

Let’s get started.

5 Reasons Your Air Conditioner is Blowing Hot Air

1. Incorrectly Set Thermostat

If your AC suddenly blows hot air, you may have an incorrectly set thermostat.

The thermostat may be out of power, accidentally set too high, set to heat, or not configured properly.

If a thermostat is set to gas heating when you use electricity, it may sound like the AC is on, when in reality it is just the HVAC fan and blower circulating air.

How to fix

Always start by checking your thermostat’s batteries and what temperature it is set to.

Check all settings to make sure the cooling option is on, and there are no settings that are interfering with the chosen temperature.

Lastly, make sure the thermostat is set to match the cooling system you have in place. Some thermostats may not have this option, and others may have a physical switch on the back of the thermostat.

2. Refrigerant Leak

An air conditioner that continues to blow warm air may be a sign of a refrigerant leak.

Refrigerant is the chemical that circulates in the AC system to cool incoming air before it is sent to the rooms in your home.

If the refrigerant levels are low, the unit cannot properly cool the incoming air and will stay on as it tries to reach the set temperature.

Because the refrigerant runs in a closed system, low levels are often indicative of a leak somewhere along the line; usually a degrading valve.

How to fix

Do not try to fix a refrigerant leak yourself.

Refrigerant is a dangerous chemical, and you will need to call a technician to correct the problem.

The technician will find the leak in the system, patch it, and top of the refrigerant again.

3. Dirty Evaporator Coils or Filter

When the air filter gets too dirty on the inside part of the AC system it blocks airflow to the evaporator coils.

The evaporator coils are the part of the AC system that removes the hot air from the house.

By blocking access to the evaporator coils, the air conditioner has no way to remove the hot air from the house. It also prevents hot air from the AC from being expelled properly.

How to fix

The easiest way to fix this problem is to prevent it from happening in the first place.

Check the air filter every couple of months and replace it when light stops passing through it well.

If the problem persists after changing or cleaning the air filter, you may need to call in a technician to professionally clean the evaporator coils.

4. Blocked Outdoor Unit

Similar to having a dirty air filter or evaporator coils, if the condenser coils on the outside unit are blocked, they cannot bring in cool air.

There should always be at least two feet of space around the outdoor air conditioning unit

Do not put plants, yard waste, compost bins, or tools in your outside unit.

Additionally, check to make sure there are no piles of leaves or grass clippings that have been sucked in.

If cool air cannot get into the condenser unit, then no cool air will get into the house.

How to fix

Clear the space around the outdoor unit to at least a two-foot gap. Do not store items next to the unit, and clean out any possible dirt or debris before trying to run it again.

Call a technician if the problem persists so that they can open it up and take a look.

5. No Power

The indoor and outdoor portion of an AC unit runs on separate circuits.

The indoor system is responsible for pushing air around your house, and the outdoor unit is responsible for cooling the incoming air.

If the breaker trips or a fuse blows, it’s likely that the outdoor unit simply no longer has power.

AC takes a lot of power, so it doesn’t take much to push your breaker over the edge.

How to fix

This issue is one of the simplest to fix. All you need to do is reset the breaker or replace the fuse.

If the breaker continues to trip, you will need either a technician or an electrician to come to take a look as there might be too much drawing from one circuit.

When to Call an HVAC Specialist?

You should always call a trained technician if:

  • The problem seems dangerous
  • You believe the problem is in a part of the system you can’t get to
  • Fixing the issue yourself would void any warranties or contracts
  • You do not have the skills or tools to do the job yourself
  • You don’t know what the problem is
  • You’re afraid you’ll make it worse
  • You think a part needs to be replaced

Depending on the issue at hand, hiring an HVAC specialist will usually cost you $150-$1300.

A refrigerant leak fix typically runs between $150-$500 depending on the location and severity of the leak in the system.

Unfortunately, making DIY repairs may not save you much. A thermostat alone costs around $50-$200.

Final Thoughts

Though many things may go wrong in an HVAC system, the thermostat, refrigerant, airflow, or power is often the culprit.

Remember, if you are unsure of what the issue is, how to proceed, or have concerns that the problem might be dangerous, don’t hesitate to call a technician.

Have issues with bugs coming through your AC? Or wondering what outside air temperature is too cold for your AC in the winter? Learn more with our in-depth guides.

About Roy Cohen

Roy Cohen has a burning passion for heating, cooling, and ventilation. He aims to help you save money on expensive repairs and bring you the best HVAC products. He has years of experience behind him in HVAC repair and garage maintenance.

You can find Roy at his LinkedIn or his email: [email protected]

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