Air Conditioner Not Blowing Cold Air but Running

If you are dealing with an air conditioner not blowing cold air but running, then this article will be helpful for you. There can be several reasons for your air conditioner not blowing cold air and these include:

  • Dead capacitor
  • Thermostat issues
  • Bad condenser fan
  • Low refrigerant
  • Dirty air filters
  • Dirty or blocked return duct
  • Blocked condenser coil
  • Dirty Evaporator coil
  • Leaks in the ductwork
  • Undersized air conditioner
  • Open door and windows
an air conditioner not blowing cold air but running
A typical air conditioner outdoor unit set up

There are among the common issues that prevent your air conditioner from cooling when it is running. Let’s now dive right into the detail.

Read also: Air Conditioner Outside Unit Not Running [Solved]

11 Reasons for An Air Conditioner Not Blowing Cold Air but Running

When your ac isn’t blowing cold air but running, you need to check whats not working with your outdoor unit. So, let’s look each of these issues that could prevent your ac from cooling.

1)Dead Capacitor

A dead capacitor will prevent your air conditioner from blowing cold air. Most air conditioners come with dual capacitors for powering both your compressor and your fan motor. However, with time any part of a capacitor can malfunction and die. Check out how to test an AC dual capacitor

If part of a capacitor that powers the compressor dies, the other part that powers the fan motor can continue running. The fan will be spinning but your ac won’t blow any cold air because of a non-functioning compressor (shortly I’ll briefly explain how a compressor helps with cooling your home)

2)Bad Condenser Fan Motor

A bad condenser fan won’t dispose the heat from the condenser coil, and this could be the reason your air conditioner is not blowing cold air. If you can hear the compressor running but the fan not spinning or turning. Try to give your fan a spin but if it’s not really spinning, give it some lubricating oil.

If your fan won’t spin when you turn on your air conditioner , the motor can get so hot that it can almost burn you when you touch.

3)Dirty Air Filters in The Air Handler

If you haven’t replaced your air filters in a long time it’s definitely a good time to replace them now. When they get dirty, they can restrict air flow to the evaporator coil. So, this will reduce the amount of cold air that blows out of the ac unit.  And if you are using the premium air filters, you’ll need to replace them on time. Premium filters are more restrictive to airflow.

4) Dirty Evaporator Coil

A dirty evaporator coil will reduce the amount of heat absorbed from your indoor air. Dirt, and other substances plugged on your evaporator will decrease the surface area of the evaporator that absorbs heat.

 While dirty air filters are a common cause for a dirty evaporator coil, this can also happen when you forget to put your air filter in.

The last thing you want is your coils getting dirty. Dirty coils are hard to clean, you will need to call HVAC professionals to come and help you clean them.

5) Dirty Condenser Coil

When your condenser unit has too much dirt, debris, and other objects blocking it, it can prevent your air conditioner from blowing cold air. The condenser unit sucks air from the sides, passing it over the coils and rejecting up. So, the air that comes in and out takes away heat from the condenser unit.

Dirty air condenser
A condenser unit that is dirty and clogged

 When the condenser unit and the condenser coil get dirty, it is very dirty, they will restrict the flow of air and heat won’t be transferred to the outdoor air. You can clean the condenser unit by spraying water. You can use the hose water to cleanse it.

6) Dirty Return Ducts

Blocked return ducts won’t be able to draw in the needed amount of air into your HVAC system. Make sure the return ducts together with air vents are not blocked. If vents are blocked or closed, cold air from your ac won’t flow freely into your home.

And if the return ducts are blocked by objects like furniture, not much air will be drawn into the HVAC systems to be cooled.

7) Thermostat Issues

Thermostat issues could be the reason your air conditioner is not working the way you expect it to.

Some of the thermostat issues that could affect your air conditioners cooling include

  1. Bad wiring. There are specific wires for every HVAC system that need to go on a specific terminal on any thermostat. If wires for cooling are not connected or are loosely connected, your air conditioner won’t turn on (no cooling.)  Try opening your thermostat, check if the Rc (power for cooling) terminal is connected. If not, jump it from the R terminal if R  terminal (for power) is connected
  2. Thermostat settings. Make sure your thermostat setting is put to cooling mode. If you use a heat pump to cool your home, you could have a problem with reverse valve. A reverse valve can stick in the heat mode. When this happens, it will not blow cold air no matter how much you try to drop down your temperature. You can call a technician who can come and replace your reverse valve.

  If your thermostat is not well calibrated, sometimes it can be batteries, you can try the thermostat by bypassing thermostat (see video)

8) AC Unit Is Low on The Refrigerant

When your air conditioner is blowing cold air when running, it could be a sign that your refrigerant has leaked out of your air conditioning system.

 The refrigerant is a chemical used in your ac system to transfer heat from your home to the outside.  The refrigerant runs in a sealed system and doesn’t not get used up like gasoline in vehicles.

Because of that, you can expect the refrigerant to last through out the lifetime of your air conditioner.

So, when you have a low charge of the refrigerant in your system, that is a good sign that there are leaks somewhere within the system.

If you believe you have a leaked-out refrigerant, I suggest you call HVAC professionals to come and assess your whole cooling system. Technicians will usually verify the refrigerant charge in your system. And if it is below the required level, they will try and pinpoint the exact source of the leaks.

9) Leaks in the Ductwork

 Leaks in the ductwork can prevent your air conditioner from blowing cold air when it is running. Air ducts are installed in areas with temperatures that are not controlled (in the attic). Variations in temperatures between seasons coupled with old age could cause ductwork to develop disconnections between them.

And if you are unlucky, when rodents find their home in your attic, they could cause considerable damage to the ductwork. They could chew the air ducts and create leaks. As cold Air passes through your ductwork that have leaks, there could be a mix of air in the attic and air in the ductwork. In short cold air could escape before reaching your leaving spaces.

Try inspecting your ductwork for problems. Ussuallyyou can fix most of these issues without the help of professionals. You may use new pieces of your ductwork to repair disconnections. Alternatively you may use metallic tape to seal off the leaks.

Also read: AC Condenser Unit Blowing Cold Air Outside [Solved]

10) Undersized AC Unit

 If your air conditioner system is way too small for your home, it will be underperforming, and you’ll feel like your ac is not blowing cold air. Some ACs installations are done without properly calculating the size of the home and the air conditioner that can fit. If you believe your air conditioner is too small for your home, there are still a few things you can do to help with cooling. So, you can try:

  • Insulating your home where there is no properly insulation.  
  • You can also try using a sealant to seal gaps between windows and between doors

11) Open Windows and Doors

Your air conditioner will not cool your home the way you expect it if your windows and doors are open. Some people think that open windows can not affect the efficiency of your air conditioner, but this is not true.

When windows are open, warmer air will always come and displace the cooler air blown out of your air conditioner. Because of that you will not feel the cool air coming out of your vents.

It’s always best to close windows and doors and seal off gaps where necessary, this is where warmer air could be passing t to get into your home.

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Final Thought

When you are dealing with an air conditioner not blowing cold air but running perfectly, there could be any number of reasons for this. But these issues we have listed in this article are the most common ones.  We hope our tips will help you greatly. If you haven’t fixed your issue or found any solutions yet, consider contacting local HVAC experts for more help. Thanks for reading.

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