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Why Is My Air Conditioner Blowing Warm Air?

by vscontent on July 21, 2017

Why is my air conditioning system (AC) blowing warm air?We’re in the middle of summer, folks! Although outdoor BBQs and pool parties are all well and good, the inside of our homes are there to provide much needed comfort and cooling.

Unfortunately, without a working air conditioning system, it’s nearly impossible to be comfortable inside your own home.

Nobody wants to receive warm air when they turn on the machine that is designed to cool you down. Luckily, if your air conditioner is blowing warm or hot air, there are a couple simple fixes that you can try first before having to call a professional.

Quickly, here are some of the main causes of an A/C that blows warm air:

  • Wrong thermostat setting
  • Dirty or improperly installed air filter
  • Leaking, undercharged, or overcharged refrigerant
  • Dirty or clogged outdoor (condenser) coils
  • Tripped breaker or blown fuse

If none of the following DIY fixes solve your problem, don’t hesitate to contact the professionals at Pacific Heating & Cooling.

How to Fix an A/C That Blows Warm Air

1. Wrong thermostat setting

Your thermostat could have been accidentally set to “heat mode”. If this is the case, there’s a simple fix. Simply flip the mode back to “cool” and see if the air conditioner cools back down.

While you are checking if the thermostat is set to “cool,” check the fan setting as well. The “auto” setting means that the fan will only turn on if the heating or air conditioning system is also on. If your fan is set to “on,” however, the fan will continue to run 24/7, even if the HVAC system is off.

If the fan is on but the air conditioning system is off, you may feel as though the air coming through your vents is “warm.” To solve this problem, turn your thermostat fan setting to “auto.”

We recommend keeping your fan setting on “auto” most of the time, and only using the “on” setting when needed.

If you can’t get the thermostat to work on your own, contact Pacific Heating & Cooling.

2. Dirty or improperly installed air filter

A dirty air filter can cause many problems for your heating and air conditioning system, which is why it is highly recommended that you replace or clean your air filter every 30 days. While some households can wait a bit longer than that to replace the air filter, never go more than 90 days without replacing the filter.

When you have dirty air filter, airflow is severely restricted, which can cause problems with your indoor evaporator coils. The indoor A/C coils need proper airflow in order to successfully absorb the warm air drawn from the home.

If there isn’t enough air passing over the evaporator coils, you may feel warm air coming from the motor instead of cold air coming from the airflow over your evaporator coils. Warm air will blow if the evaporator coils or the filter are severely blocked by dirt and debris.

The solution is to remember to check and/or change your air filter every 30 days. Go to your air filter right now and replace it if it is dirty. Set reminders on your phone or calendar so you never forget this important HVAC maintenance task.

If the coils are the cause of the dirty filter, they will need to be professionally cleaned. Never try to clean your evaporator coils unless you are a certified HVAC technician. Contact Pacific Heating & Cooling for an evaporator coil cleaning with a full system inspection and maintenance.

3. Leaking, undercharged, or overcharged refrigerant

Refrigerant is a common culprit for A/Cs that blow warm air. If your air conditioner is low on refrigerant/Freon, it will likely blow hot air.  The system might not have the appropriate refrigerant charge (check to see if there is ice forming on the units, if so, the system probably doesn’t have enough refrigerant). Or, there could be a refrigerant leak in the system.

Refrigerant is highly dangerous and should only be handled by professionals. If you believe the issue is due to leaking, undercharged, or overcharged refrigerant, contact a certified HVAC technician for the proper services.

4. Dirty or clogged outdoor (condenser) coils

If you’ve checked the thermostat and the air filter, but warm air continues to flow through your air ducts, you’ll want to check the outdoor HVAC unit next. The condenser coil on the outside unit needs to be properly maintained in order to preserve the operation of the entire system.

If the coil is blocked by outside dirt and debris, see what you can do to alleviate that burden. Remove larger pieces of debris by hand and consider rinsing the unit off with your garden hose (turn off power to the unit first). Make sure that the water flow is gentle—heavy blasts of water can bend your condenser coil fins.

Use this time to look for signs of oil or coolant leaks. If you spot dark drip marks or leaking liquid, contact a professional.

You can also try vacuuming the outdoor coils with a soft brush attachment. Again, be careful not to bend or damage the vulnerable fins.

Bent fins hinder airflow. If you notice a lot of bent condenser coil fins, it’s best to call a professional to straighten them out. Never try to straighten them with a crude object, such as a knife or screwdriver. You can, however, purchase fin combs that do a pretty good job at straightening the fins. Learn more about the importance of keeping your condenser coils clean.

Calling your local HVAC company for annual professional condenser coil cleanings is the best way to prevent your air conditioner from blowing warm air. Call for annual air conditioning maintenance in spring so that you have a clean, unclogged system when summer starts.

5. Tripped breaker or blown fuse

The last thing you want to check is your circuit breaker or fuse box to make sure that the outside unit is getting supplied with electricity.

If the outdoor unit has tripped the breaker or blown the fuse, your indoor unit will continue to blow air, but it won’t be cold air since the outdoor unit isn’t on. To fix this problem, check your electrical panel.

If you have a circuit breaker, turn the tripped breaker completely “off” before switching it to the “on” position.

If you have a fuse box, replace the blown fuse with a replacement fuse that matches the amperage rating of the circuit.

A dirty condenser unit and leaking refrigerant are often the reason behind your air conditioner blowing warm air in the summer. Annual HVAC maintenance at the beginning of each season change and periodic condenser coil cleanings will help keep your system at peak performance.

For more information on how to care for your HVAC system this summer and all year round, don’t hesitate to contact Pacific Heating & Cooling.