Troubleshooting an Air Conditioner that is Not Blowing Cold Air

Troubles with an air conditioner are never great, but it is especially a problem when it seems your air conditioner is making your home warmer! There is never a worse time to discover that your AC is blowing warm air than the middle of a hot Kansas summer.

When you realize your air conditioner is putting out warm air instead of cool air, what should you do? It may seem like your system is completely broken and that you will need a costly repair or even an even more expensive complete AC replacement. But the good news is that isn’t always the case. There may be some easy fix that just about any homeowner can handle to get the hot air problem fixed right away.

What Should You Do When Your AC is Blowing Warm Air?

The first thing you should NOT do is panic and rush for the phone to call for a repair. Yes, we would be happy to fix your air conditioning problem whenever you need us, but if there is an easy fix, doing it yourself will save you some time and money. So before calling a professional technician, we want to give you the AC Blowing Warm Air Troubleshooting Tips you should try first. 

Here at Standard Plumbing, Heating & Air, we receive calls throughout the summer from Manhattan, Wamego, Junction City, and surrounding towns with people in distress over a broken air conditioner. Sometimes when we go to service their AC system, we discover the source of the problem required easy fixes the homeowners may have been able to handle themselves.

Troubleshooting AC Blowing Warm Air

Here are the first steps for a homeowner to take when faced with an air conditioner is not blowing cool air. These are pretty basic steps that just about anyone at any skill level can handle.

These troubleshooting steps: 

  • Are relatively easy and require no (or little) repair skills
  • Can be done quickly, often in mere minutes
  • Require little or no money

Taking a little bit of time to troubleshoot your AC problem could really pay off. If one of these troubleshooting steps fixes your problems, you will have prevented paying for a service call.

Graphic image showing the 4 basic troubleshooting steps to do when your AC is blowing warm air


You are going to hope the thermostat is your problem because it can be the easiest problem to fix! Getting your air conditioner to blow cool air again may be as simple as a push of a button.

We see this problem every so often: someone in the home changes the thermostat. Whether they intentionally wanted it much warmer or simply hit something wrong by accident, there could be a setting that is making your AC blow warm air.

Checking to ensure that your thermostat settings are where they should be is your first step.                 

Is the thermostat set to COOL? No matter how low you set your thermostat it, if it’s not at the COOL setting, it won’t put out cool air. You need to make sure the thermostat is indeed set on COOL. It should not be only on FAN or HEAT.

Is the thermostat set to be colder than the current temperature? If you haven’t adjusted your thermostat since the winter, it may be set to a hotter temperature than the ambient temperature. If that’s the case, lower the set temperature to be a number below the current air temperature. You should notice your air conditioner fan kick on rather quickly. And soon after, you should feel cool air coming from your vents.

Is the thermostat’s battery dead? A lot of us forget that the device controlling our temperatures needs battery power to work. If that battery is dead, it can’t send the message to your HVAC system the message that your house is too hot. It is great news if you discover this is your problem. Simply replacing your thermostat’s batteries may be all the fix you need to get your air conditioner back to working and blowing out cool air.


This step is to simply check all the vents in your home. Are your vents open? For proper heating and cooling to occur, you need to keep every vent in your home open. It’s a common mistaken belief that closing vents to rooms saves energy. However, your HVAC system was designed to work in the way it was set up, including utilizing your full duct work system. Vents should be open for proper flow of air through your home. It is okay, however, if a couple vents are closed.

Make sure you can feel air coming out of your registers. If you do not feel any, the fan motor in your HVAC system may not be working. Call us at Standard and our technicians can get that fixed quickly.


Your home’s HVAC includes a component of the AC system called an evaporator. The evaporator absorbs heat from the air and transfers it to your outdoor AC unit (the condenser). To check this step, go to your furnace and listen if the blower motor is running. Also, check to see if there is any ice on the evaporator coil. That may indicate there is a refrigerant leak or something simpler to address such as a dirty air filter (keep reading for more on air filters).

If your evaporator mower is not working, you will want to contact a professional air conditioning technician to handle. There are a few issues that could be keeping the motor from working, from lack of lubrication to electrical issues, and these are most safely handled by a trained technician.

Dirty air filter:  This is a great problem to discover as it is very easy to fix. You may not have realized exactly how important it is to change your air filter on a regular schedule. It’s the most important part of regular AC maintenance. Many people don’t know how frequently it needs to be changed or the serious problems a dirty filter can cause. A dirty or clogged filter really can shut your entire HVAC system. If your air filter looks dirty, change it. That alone may be the only fix your air conditioner needs to begin blowing cool air again!

While the indoor component of your cooling system contains the fan that blows air through your home, it will blow air even when the outside unit is not working. It is your outside unit (the condenser) that turns the air cool that gets circulated through your home. That takes us to Step #4.  


If you’ve tried the above 3 troubleshooting AC steps and your vents are still blowing warm air, it’s time to go outside.

Look at the outdoor AC unit. Does it have any frost or ice on it? If it does, change the setting on your thermostat from COOL to having only the FAN on. This will allow the unit to thaw. It may take as much as 12 hours for the unit thaw out. A frozen outdoor AC unit is often an indicator that your air filter needs to be changed. If changing your filter fixes the problem, but only temporarily, you may be dealing with a possible freon leak. Contact Standard and our technicians will quickly come out to resolve any potentially dangerous freon leak. We will also refill your unit with refrigerant.

Another thing to check is whether the unit is dirty. It’s common, especially here in Kansas, to find our outdoor AC unit covered with milkweed, leaves or other natural debris. If you can see it is dirty, you can clean it.

How to Clean Your AC Condenser Unit 

    • Turn off your condenser unit.
    • Remove the top section and outer caging.
    • Spray the coils from inside the condenser with a hose. Make sure you are spraying from the inside going out. Do not spray from the outside in. Also, take care to not bend the fins.

If you want a professional to handle the cleaning and maintenance of your AC unit, feel free to schedule service with us online or by calling at (785) 776-5012.

Graphic image showing the list of big AC problems that would require an HVAC technician, such as one from Standard Plumbing, Heating & Air Conditioning in Manhattan

Other Broken AC Problems

If none of the above AC Blowing Warm Air Troubleshooting Steps worked for you, call us. We may be able to provide you more things to check that can be handled on your own. Give us a call at (785) 776-5012. We will be happy to come out and service your HVAC unit to get cold air blowing again as soon as possible.

You can learn more about how air conditioners work and energy saving tips from the U.S. Department of Energy.