Why Is My Air Conditioner Blowing Warm Air?

April 10, 2024

Nothing provides respite from the California heat like cranking the AC. But when San Jose temperatures threaten to break records, your AC blowing warm air becomes much more than an inconvenience.

Warm air from your HVAC unit can signal issues with your system that can lead to bigger problems. Learn the warning signs of an AC breakdown and when to call our HVAC pros at Service Champions.

DIY AC Troubleshooting Tips

With these AC troubleshooting tips, you can resolve small fixes on your own and learn when to call the pros.

Adjust the thermostat

If your AC is blowing warm air, your thermostat may have accidentally switched to heat. Flip the thermostat setting back to cool and to the correct temperature, between 60 and 75 degrees. If you have a programmable thermostat, check that the temperatures are correct.

If the thermostat lacks power, swap dead batteries for a fresh set. Issues such as a glitchy screen, poor wiring, and debris buildup may require more advanced repairs from an HVAC technician.

Check for a flipped circuit breaker

HVAC units and other appliances require a lot of power to run, and excessive power demand can trip the circuit and shut off power as a safety precaution. Locate your electrical panel and look for a tripped breaker or a blown fuse, which should be flipped to the center and may show a red or yellow tab. To turn the power back on to the unit, flip the breaker completely off and to the opposite direction of the other breakers, then flip it on.

If resetting the breaker doesn’t restore power, contact your utility company to check for recent power outages. Check for signs of a blown fuse, such as cracks or ash. 

While you can find fuses in hardware stores and replace them yourself, remember that working with live electricity requires certain safety protocols. An electrician can safely swap out your fuses and identify any other issues with your electrical system, such as worn-out breakers, bad outlets, or circuit overloads.

Inspect the evaporator coil and air filter

Airflow through your vents, ducts, and air filter can harm your AC system. Air filters gradually accumulate dirt and debris and can eventually clog, and vents and ducts can gather debris and block airflow. A clogged air filter can also result in dirt accumulation on the evaporator coil, which limits the heat exchange necessary for proper cooling. Dirty coils are unable to properly absorb heat from the air and can freeze over and inhibit cold airflow altogether.

Depending on your climate, filter type, and household conditions, you should replace your filter at least every three months. You can usually find the air filter near the air handler or return duct. Replace it with a new filter according to the directions in your user manual. If you suspect your ducts or vents have clogs, look for vents with limited airflow and listen for strange noises to locate blockages, removing them if accessible. 

If your evaporator coil is frozen, turn the AC system off, change the air filter if necessary, and allow the evaporator coil to thaw before turning it back on. If the coils freeze again, turn the unit off and call a professional HVAC technician to look for more complex issues, such as inaccessible ductwork blockages, compressor malfunctions, or refrigerant leaks.

Clean the condenser coil

Most AC systems include an outdoor condenser unit with a coil wrapped around it. If debris has clogged the condenser coil, the unit won’t be able to draw heat from your home as effectively or at all, potentially resulting in limited cold airflow, poor energy efficiency, and damage to the unit itself.

If your condenser coil unit clogs, turn off the unit at the source. Remove accessible blockages with gloved hands, and gently rinse off the smaller debris with a hose. An HVAC technician can also clean the unit during regular maintenance and they can also check the fans, capacitors, and other parts that may require more complex solutions.

Look for refrigerant leaks

Refrigerant is a crucial part of the cooling process that draws heat and humidity from indoor air, and low or leaking refrigerant can quickly result in long cooling cycles, an overworking unit, and the HVAC system blowing hot air. Even with proper maintenance, metal erosion, cracks, or defects can result in leaks, which are sometimes hidden.

Refrigerant is a hazardous substance and should be handled by a qualified technician as soon as you notice signs of leaks, such as hissing or gurgling noises, chemical smells, or ice on the refrigerant line.

Summer Air Conditioning Tips:

To keep your AC cooling efficiently all summer, try these tips:

  • Sign up for a home maintenance plan so you never forget annual tune-up appointments.

  • Program your thermostat to cool less when you’re away.

  • Use your ceiling fan.

  • Prevent moisture problems with proper ventilation.

  • Keep doors and windows closed when running the air conditioner.

  • Clean and dust your home regularly.

When To Call a Professional HVAC Technician

While you can resolve many common causes of your AC blowing warm air with DIY strategies, most tasks are better left to the pros. Your AC system is made up of complex mechanisms and parts, and taking on repairs without the right HVAC knowledge can result in further damage and higher repair costs.

Our HVAC technicians are equipped with the appropriate education, skills, and experience so they can efficiently diagnose and repair issues when your air conditioner isn’t cooling. They can also confirm that your AC unit matches the square footage of your home and recommend any replacements or upgrades.

Get Your AC Unit Ready for California’s Summer Heat

While pool parties are a great way to enjoy California’s summer temperatures, they’re not always enough to take the edge off. If your AC isn’t cooling, a professional service can help return refreshing air to your home.

With more than 200,000 satisfied clients served throughout the East Bay, South Bay, and Sacramento areas, our technicians at Service Champions are always up to any HVAC job. Contact us today or book online to take advantage of easy payment plans and award-winning service.


How long are AC cooling cycles?

On an average San Jose or Sacramento summer day, AC cooling cycles should last about 15 minutes. Cycles regularly lasting 30 minutes or longer may indicate a problem with your system.

What happens if AC runs too long?

If your unit runs too often each day, you can expect higher energy bills. Excessive running can also cause wear on your unit, potentially shortening its lifespan.

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