How To Fix An Air Conditioner Blowing Warm Air

How To Fix An Air Conditioner Blowing Warm Air

If you are asking why is my air conditioner blowing warm air then this post will help you find and fix the reason.

There are several reasons why this may be happening. I will go over some of the obvious ones that are simple to troubleshoot and repair.

The first mistake people make is to assume that the system is low on refrigerant. Your HVAC system may be low on refrigerant but that is not where you should start.

*Read the Disclaimer at the bottom of the page.

There are parts of the system that can become restricted and will cause the air to blow warm. Quite often a technician will connect his gauges before checking other components and tell the homeowner the Refrigerant is low.

If the indoor filter is really dirty it will cause the readings on a set of A/C Gauges to read the wrong refrigerant levels. When the evaporator coil is dirty it will cause the Air Conditioner to underperform and possibly blow warm air. The outside condenser coil also needs to be clean and free of restrictions.

  • Dirty Air Filter
  • A Dirty Condenser Coil
  • Dirty Evaporator Coil
  • Drain Line Issues
  • Refrigerant Level

The point I’m making is don’t just check or assume low Refrigerant is the reason your air conditioner is blowing warm air.

A Dirty Air Filter

A dirty air filter will restrict the airflow and cause your air conditioner to blow warm air. Sometimes the evaporator coil will freeze up when the air filter is really dirty. When this happens you will need to let the ice on the evaporator coil melt before you turn the system back on.

After you remove the clogged filter and replace it with a new one turn the system back on. If you wait 5 minutes you should feel cold air coming out of the register. If this was not the reason your air conditioner was blowing cold air then you will need to move on to the next item to look at.

Dirty Condenser Coil

Another possible reason your air conditioner is blowing warm air is that the outdoor condenser coil is dirty or somehow restricted. You should easily be able to look at the condenser coils to determine if they are dirty. Air needs to be able to flow through the coils in order for the HVAC system to function properly.

Dirty evaporator coil causing warm air to blow
Dirty Condenser Coil

If plastic gets stuck on the outside of the condenser coil or if other items such as bushes or shrubs get really close to the coil it will restrict the airflow.

If the coil is dirty you can take your hose and use low pressure to clean the coils of any debris.


High pressure will bend the coils and cause poor airflow problems. So, only use low pressure and wash the coils off.

Don’t use any type of brush or anything like that. Local home improvement stores like Home Depot or Lowes have coil cleaners that you can use to clean the coils.

The goal here is to clean them not harm them. I have heard and seen people use products that deteriorate the coils. Make sure to use a NON-ACIDIC cleaner that’s approved for A/C coils.

After you clean the condenser coils turn the system back on and wait 5 minutes to feel if cold air is coming out of the register. If cold air is coming out then great. However, if cold air isn’t coming out then you will need to move on to the next step.

A Dirty Evaporator Coil May Be The Reason Why Is Your Air Conditioner Blowing Warm Air

Your evaporator coil is inside near your blower motor. If your evaporator coil is dirty it may cause the air to blow warm on your air conditioning system. Depending on if you have a furnace or an air handler will determine what [access covers] you need to remove to access the evaporator coil.

You are wanting to see the side of the evaporator coil that air flowing into. Whatever direction the air is flowing is the section of the evaporator coil you want to look at.

Dirty evaporator coil causing warm air to blow
Dirty evaporator coil causing warm air to blow

In some scenarios, your system may have an access door near the evaporator coil. If this is the case you can open the small access door and look at the coil.

If the coil is dirty you will need to clean it.

The same rules and methods apply to your evaporator coil as the condenser coil.

You don’t want to use any brush or anything like that. You want to use an approved cleaner and possibly a hose to clean the coil. make sure to let the cleaner sit for a while to loosen up the impacted dust.

after it sits for a while have a squeeze trigger on the end of the hose and apply a little pressure. to clean the evaporator coil.

If you take your time the water will simply go into the evaporator coil pan and drain out of the home. This way you don’t need to worry about water damaging your property.

after you have cleaned the coil you should put all of the covers back on and then turn the system on. Let the system run for a good 5 minutes to see if cold air comes out.

If you still don’t have any cold air you will need to move on to the next step.

At this point, you have cleaned the major parts and the system should be blowing cold air. If the system is not blowing cold air but everything else seems to be fully functional then it’s time to check the refrigerant level.

Drain Line Issues

Wherever your evaporator coil is located you will find the condensation drain lines. They will be white and the typical standard size is 3/4″ in size. Different systems have different configurations.

How can a drain line cause warm air to blow? I will fill you in on a little secret.

When some systems are installed they put in a safety overflow switch. this is a switch that is typically close to the evaporator coil.

When the drain line is clogged the water will back up causing the safety switch to shut only the outside condenser off. It should shut the whole system off but in this scenario, they wired the system so the outdoor shut off and the indoor keeps running.

When this happens the inside unit runs as normal but it only blows warm air. I have found this so many times on service calls.

Here is a picture of what the safety overflow switch looks like. All you have to do is take the cap off and then clear the drain line.

why is my air conditioner blowing warm air.
Overflow Safety switch

You should know if this was the problem right away because when you pop the cap off you will see water backed up.

After you clear the drain line put the safety overflow switch in place and start the system up.

If after doing all of the other steps without any cold air coming out then you clear the drain and cold air come out you know you fixed your problem.

Refrigerant Level

If all of the other attempts to fix Why Is Your Air Conditioner Blowing Warm Air did not work then you will have to connect an approved set of Gauges to get the readings on the system. After connecting the gauges you know the system is clean and should be giving accurate readings.

At this point, you will be able to determine if something more serious is wrong with your system. I hope this post helped determine why your air conditioner is blowing warm air.

Routine Services Your A/C And Heating Equipment Needs to prevent it from blowing warm air.

Here are the top 10

How to fix an air conditioner blowing warm air and what routine services your a/c and heating equipment needs work in conjunction in many ways.

You need to keep your HVAC equipment operating at tip-top energy efficiency to prevent costly breakdowns and to prevent your system from all of a sudden blowing warm air.

The top 10 are not in order of importance. Like most equipment that works together as a system if one part of your HVAC system isn’t working well or is dirty it will affect other parts of the system.

#1 Clean Evaporator Coil

Evaporator coils need to have routine cleanings and adjustments done in order to keep them operating at their peak performance.

How To Fix An Air Conditioner Blowing Warm Air

The evaporator coil has a refrigerant that is responsible for absorbing the heat and humidity in your home’s air.

When your evaporator coil becomes dirty from dust impacting between the fins it drastically reduces the ability for your air conditioning or heat pump system to operate how it needs to.

Many homeowners don’t notice a big difference in the performance of their Air Conditioner or heater until they have a major breakdown.

The reason people don’t notice a difference in the performance of the evaporator coil is because performance loss happens over time. The dust and moisture slowly clog the normal path the air would take allowing the refrigerant to absorb the heat.

How To Fix An Air Conditioner Blowing Warm Air
How To Fix An Air Conditioner Blowing Warm Air

Because the air cant go through the normal path the air will divert and the refrigerant doesn’t have an opportunity to absorb the heat as it should.

The vast majority of residential split system ac system evaporator coils in Slidell, LA homes are enclosed in housing. For this reason, the evaporator coil is out of sight and out of mind and usually goes many years without being cleaned.

While performing routine maintenance and service in Slidell, La I’m often asked how often should an evaporator coil in Slidell be cleaned. My answer is, it all depends.

I think at a minimum every home should have the evaporator coil professionally cleaned 1 time per year.

But if you live closer to water and have multiple pets and an inadequate filter system you may need it cleaned multiple times per year.

#2 Clean Condenser Coil

If your house in Slidell has a typical split system then your condenser coil will be located outside.

When the refrigerant inside your evaporator coil absorbs the heat the refrigerant will become a vehicle and carry the heat and humidity outside to the condenser.

The condenser coil fins need to be free of debris in order for the air to pass over the coil and create the process where the heat that was absorbed by the refrigerant can be released outside.

Your condenser coil is subject to all the elements outside.

How To Fix An Air Conditioner Blowing Warm Air and have it blowing cold quickly

Every time the condenser turns on air is being sucked through the fins. The air will include dust, pollen, grass clippings, and many other items that can and will get stuck in the fins.

I have found Leaves, dust, dirt, insects, and dead animals inside the condenser coil.

By having the condenser coil professionally cleaned your condenser will be able to perform at its optimum performance keeping your utility bill low and extending the life of your system.

#3 Proper Refrigerant Amount

Having the correct amount of refrigerant in your air conditioner or heat pump system is very important for your system to operate at its full potential.

If you live in Slidell, LA then you know how hot and humid it can get. Many of the homes I service in Slidell don’t have adequate insulation in the attic or inside the exterior walls, so having your refrigerant level exactly where it needs to be is very important.

Having a professional service company with the correct equipment to accurately measure multiple data that affects the performance of your system is extremely important.

Many of the homes that are serviced here in Slidell are over-charged with refrigerants. Most often the system is over-charged because of technician error.

How To Fix An Air Conditioner Blowing Warm Air
How To Fix An Air Conditioner Blowing Warm Air by adding the correct amount of refrigerant

Many technicians will immediately suggest to a homeowner that the system needs refrigerant or as it’s commonly called by a brand name “FREON.”

This should not be the first recommendation given by professionals until they have checked many of the other factors that can contribute to the appearance of the refrigerant being low or high on gauges.

Technician’s readings can be misleading if the airflow is restricted in some way in the HVAC system.

For this reason, I find many of the systems I connect my gauges to overcharge.

Having an HVAC system over or undercharged is bad and will hinder the performance and life of the system.

If everything else is correctly sized and installed correctly on the system but, the refrigerant is just low then a leak test will need to be performed to ensure no leak is present.

The refrigerant is the vehicle that carries the heat outside, so when the refrigerant is low there is less of the vehicle to carry the required amount of heat.

Having a professional that has experience with mismatched equipment and undersized ducts and many other factors to determine if your system is accurately charged is so important.

#4 Cleaning the blower motor are routine services your a/c and heating equipment needs.

Having a clean blower motor on your system probably doesn’t seem very important but it is. When a blower motor hasn’t had a professional cleaning in a while. Dust will impact the high-velocity spinning blades and become impacted and hard.

After the dust impacts the blades it reduces the ability for the blades to catch and move the air correctly.

The Top 10 Routine Services Your A/C And Heating Equipment Needs.

Even small amounts of impacted debris on the fan blades will reduce the life of the blower motor and reduce the ability of the blower fan to move air in the home.

Most blower motors require the removal of electrical wires from the control board and other mechanical things that must be removed in order to be properly cleaned.

This should be done by a professional that has worked on and has experience shutting off all the power and making sure to not damage or bend any of the components during removal.

#5 Primary & Secondary Drain Line

The primary and secondary drain lines should be routinely cleaned out and checked to ensure the free flow of the condensation coming from the evaporator coil.

When air flows past the evaporator coil it carries dust and other elements in that air. When that air hits the evaporator coil some of that debris gets in the coil and in the evaporator coil drain pan. Not the emergency pan but, the internal drain pan inside the evaporator coil enclosure.

Slidell la air conditioning service and repair

Ague and other dust will collect in the drain pan and work its way into the drain line.

If a professional company is servicing your equipment they should be doing what’s required to ensure the drain pan and primary drain line don’t clog up.

Living in Slidell, La adds to the number of algae build in the evaporator coil. I have found that due to the proximity of Lake Ponchartrain routine maintenance on the evaporator coil and cleaning of the evaporator coil pan and drain lines are required.

#6 Capacitors

Your system may have a few capacitors that need to be checked to make sure they are still strong enough and haven’t gone below the manufacture’s suggested replacement.

The capacitor will have a sticker on the side of it that tells you what size in Microfarads.

For example, if you have a dual run capacitor it may be a 40/5 MFD capacitor. The 40 MFD is used to assist the compressor and the 5 MFD is used to assist the condenser fan motor. The sticker will give an allowable % below the original rating that is allowable.

For example, if your capacitor is the 40/5 and you use the tester and it only reads 30/2 then the capacitor should be changed out. Even if the condenser is still operational you should change out the capacitor to prevent any of the other components from being damaged due to overload.

routine services your a/c and heating equipment needs

I prefer to test capacitors under load. Testing in that manner should only be done by a trained professional. However, there are capacitor testers that make it fairly simple for a mechanically inclined person who has the time to check the capacitor.

The indoor blower motor will often have a single-run capacitor also. Sometimes they are fairly hard to access and may even require the blower motor to be removed in order to test it.

Having your capacitors checked and replaced before they completely go out is something that needs to be checked on a routine basis.

#7 Compressor And Motor Amps How To Fix An Air Conditioner Blowing Warm Air may be directly related to over-amping.

Your compressor and blower motors have nameplates that list the amps and volts the motors should be operating under.

The Top 10 Routine Services Your A/C And Heating Equipment Needs.
routine services your a/c and heating equipment needs

By checking the Amps routinely you can catch small problems before they get big and expensive.

When your service provider has a detailed history of what the amperage of your motors was from the previous visits they will know if something is causing a problem if the amps are getting higher than normal.

#8 Refrigerant leaks

Checking for refrigerant leaks can save a compressor from overheating and prevent costly refrigerant from leaking into the atmosphere.

Some leaks in Slidell, LA A/C systems start as small leaks from a loose fitting or an aged and rusted section of the evaporator coil.

ac repairs in slidell la

By catching the leak early, you may prevent your system from freezing up and further damaging your system.

#9 The Contactor

On a routine check of the A/C system, you need to check the contactor to make sure it’s not sticking. Sticking can occur when the thermostat calls for cooling and the metal contacts are so damaged they overheat and stick together.

routine services your a/c and heating equipment needs
routine services your a/c and heating equipment needs

When they stick the condenser may keep running even when the inside has reached the set temperature inside. This can cause numerous problems and premature failure of the compressor.

#10 Return And Supply Static pressure are routine services your a/c and heating equipment needs

Checking the return and supply static pressure will reveal a lot of information about your Slidell, LA HVAC system.

If your static pressure hasn’t been checked before it may reveal inadequate return air-flow. The return air is where the air flows through the filter and gets conditioned by the A/C system.

The Top 10 Routine Services Your A/C And Heating Equipment Needs.
routine services your a/c and heating equipment needs

If your HVAC system has inadequate return airflow then another return air will need to be added to allow your system to operate to its full potential. This isn’t 100% necessary however it is required if you want lower utility bills and to prevent excess wear and tear on your Slidell air conditioner and heater.

A static test may reveal the supply ducts are not large enough or they may be too large.

If your service provider is checking the static pressure often then you most likely already know if major issues exist.

By checking on a routine basis you will ensure the static numbers stay good by having a clean filter and system sized correctly and allowing the air to flow freely.

There are many other items that can be added to the list but I wanted to give you my top 10. Have your system routinely maintained by a qualified professional.

If this information provided any value please leave a comment below.


* WARNING! This post and information on this website are for trained and certified technicians only. It is for educational purposes only. Under no circumstances should anyone who is not qualified or have the required permits or licensing attempt to use any information in this post to try and repair an HVAC or electrical system on their own. The opinions and methods I use are my opinions and I give no guarantee of any type of outcome. In other words, if you are not a trained and certified technician you should not attempt any repairs on your own. You should hire a licensed professional to do the work.  

*Income & Affiliate Disclaimer. If you purchase a product or service from one of the links on this page you should assume I earn an affiliate commission. Meaning I earn money because you purchase through one of my links. You should also assume that by clicking on my links you may receive email communications from me. 

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