Why Your AC Blows Warm Air

Your air conditioning unit has one job: to blow cold air. When it suddenly stops doing that, it’s not just uncomfortable, it’s downright annoying. What would cause an air conditioner to blow warm air? Is it something that’s easy to rectify, or do you need to call in a professional to fix it?


The first thing to check is your thermostat. If your thermostat has accidentally been set to heat, it will definitely cause warm air to blow from the vents. On the other hand, even if your system is set to cool and not heat, if it’s turned to “on” instead of “auto”, it means that your system will be blowing air all the time, whether or not the air conditioner is actively cooling that air. It’s better to keep it on the “auto” setting so that the system will run more efficiently.

If the thermostat isn’t the issue, something may need cleaning. Have you been changing your air filters as often as you should? Most filters should be changed monthly, and if you don’t keep up with that small maintenance step, the filter can become dirty and clogged. This will block the air circulation in your system, which could cause it to blow warm air. Another component that may require cleaning is the evaporator coils. You can clean these yourself, by turning off your AC, removing the outer panel, and cleaning the coils with compressed air, a brush, mild detergent, or a commercial cleaner. On the other hand, it may be easier to call in a professional to do the job.

Don’t forget that part of your HVAC system is outside. If the outside condenser unit isn’t properly maintained, it may be causing the problem. Go look at it and see if something is blocking the condenser coil’s air flow, like dirt or debris. It’s important to maintain the outside unit, cleaning the condenser coils during the summer as often as necessary. Another problem that can occur with the outside unit is a loss of power. Even if the indoor part of the HVAC is working, if the outside unit has lost power, the air won’t be cold. Check to see if a fuse has blown or a circuit breaker has been tripped, and call a professional immediately if this is the case. It could indicate a serious problem with your air conditioner.

Electrical issues can be a problem. Running an air conditioning unit requires a lot of power. If any part of your unit isn’t receiving electricity, the whole unit can malfunction. If you suspect an electrical problem, call for a repair immediately.

Your ducts may also be causing the problem. Sometimes, ductwork gets knocked out of place and becomes disconnected. When that happens, it’s no longer sealed, and it can let hot air into your house. Call a professional HVAC technician, to ascertain whether your ducts need to be repaired or replaced.

Your system may need refrigerant/Freon. The way that your air conditioning system cools the air is by moving refrigerant, usually Freon. If there’s a leak that’s allowing this refrigerant to escape, the AC will stop blowing cold air and start blowing warm air. Other signs of leaking refrigerant include ice forming on your AC unit, and a buzzing or screaming sound. If you suspect you have a Freon leak, call for professional assistance immediately, as refrigerant can be harmful to your family’s health.

Of course, the best way to ensure that none of these problems disrupt your summer air conditioning is to keep your system in good repair through regular maintenance. As already discussed, part of this is keeping your outside unit free of debris and changing your air filters regularly. Another big piece of the puzzle, though, is professional preventative maintenance. Each spring, before you crank up your system for the first time in the summer, have an HVAC professional come out to check your unit for problems and make sure everything is in good working order.

During this maintenance visit, the HVAC technician will inspect the belts, thermostat, and refrigerants, and check for duct leakage. He or she will also perform services like blowing out the lines and checking the safety controls. The technician will tighten electrical connections, lubricate the moving parts, and check and inspect the condensate drain. In addition, the evaporator and condenser air conditioning coils will be cleaned to help the system work more effectively. Any adjustments that need to be made to your system to help it work efficiently will be done, and parts that are preventing it from working the way it should will be replaced. Your HVAC professional can also advise you on any other work that should be done, such as cleaning out the air ducts. If your system needs an upgrade, your technician can offer advice on that as well.

If you need to find a professional to check your HVAC, or you’re in the market for air duct cleaning, repair, and replacement services in Tampa, St. Petersburg and the surrounding area, please feel free to call Air Rescue at (813) 375-9982. Since 1946, our family-owned business has been providing superior service at unbeatable prices, offering heat and air conditioning repair services, new HVAC system installations, and more for homes and businesses. The service team at Air Rescue Air Conditioning consists of 75 expertly trained and licensed technicians, who work quickly and efficiently. Our service and pricing guarantee ensures that we always arrive on time, offer you the lowest price in the industry, and leave you 100% satisfied. Schedule your service visit today, and we’re confident that you’ll make us our HVAC company for life.

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