Air Conditioner Not Cooling, Hot Copper Pipe

copper pipes on air conditioner

On a hot day when the AC is on and working, the copper pipe connected to the unit should be cold to the touch and possibly sweating. If the air conditioner is not cooling and you have a hot copper pipe, you have a problem with the AC that you need to fix.

A hot copper pipe is a bad sign for an AC unit and usually, this means your air conditioner is not cooling properly. The copper line is the suction line for the system, and it should be cool because it helps to supply the cool air your AC is using to cool down your home.

How Your AC Works

Split air conditioners and mini-split air conditioners use copper pipes, sometimes aluminum pipes, to supply the refrigerant that cools the air.

Other types of air conditioning systems, such as window units, portable AC units, and through-the-wall air conditioners, do not use copper pipes to carry coolant.

In split systems that have copper or aluminum pipes, there are two units: an indoor blower and an outdoor compressor.

Mini-split systems do not push air through ducts and through vents to cool the entire home the way that standard split systems do. Rather, they provide air to blowers that push cool air into specific rooms and small areas of the home.

The compressor holds the coolant. A fan pushes the coolant through the copper pipe, which connects the compressor to the blower inside.

This coolant goes over coils, through the copper pipe, and into the blower, where the coolant cools down the air in the home.

A hot copper pipe means that the coolant is not traveling through the system properly and therefore, it is not cooling the air.

What Do AC Copper Pipes Do?

In an air conditioning unit, copper piping is used to carry the refrigerant from the compressor to the blower. This refrigerant is the stuff that actually creates the cool air that is dispersed into your home, so a hot copper pipe is going to produce warm air instead of the cool air you want.

If these pipes are hot, you are not going to be getting cool air in your home and you definitely have some kind of problem. Since refrigerant is supposed to be conducted through these pipes, the pipes should be cool to the touch as long as the AC is on by default.

AC Blowing Hot Air

When the AC is blowing hot air instead of cool air, it's very confusing. Everything is suddenly backward.

Warm air, particularly when coupled with a hot copper pipe, can indicate a few specific problems with the air conditioning system. If you can figure out which one of these problems is causing the heat in the pipe, you can potentially fix it and get your AC running the right way again.


When something goes wrong with the air conditioner, it’s only natural to suspect the coolant is causing the problem. Low coolant levels are a common problem in AC systems and when the coolant is low, the air may not blow as cool as you want it to.

But when refrigerant levels are low, the copper pipes don't get hot. Low coolant levels will actually cause the pipes to get very cold and possibly even freeze.

So if your copper pipe is hot, low refrigerant is the least like culprit of this issue. However, there are some other AC problems that can cause hot air to flow through the pipes, instead of cool refrigerant.

However, the pipe could become warm or possibly even hot if the air conditioner has received too much coolant. When the AC has got too much refrigerant in it, the air blowing inside from the air conditioner will be warm.

This is known as overcharging, and it causes everything in the AC system to have more pressure, use more energy, and work a little bit harder. Oddly, this often has the effect of making the air condition blow hotter air, rather than cooler air.

When refrigerant levels are low, the pipe is more apt to freeze. When refrigerant levels are too high, the pipe is more likely to get warm.

This might seem a bit backward, but this can be an effective way to zero in on the coolant problem you are having if coolant levels are negatively affecting your air conditioner.


The compressor is responsible for moving the refrigerant through the AC system. This is the part of the system that is outside the house, and there are a few different things that can go wrong with this unit that will cause the copper pipe to get hot and prevent cool air from blowing inside your home.

If the compressor isn't getting enough power or it's clogged with debris, the refrigerant won't be sent through the system, and warm air will blow through the pipes instead.

A clog in the compressor or anything else that is impeding the airflow will cause the compressor to run, which means the motor is getting hot, but it’s not drawing in the air it needs in order to provide cool air inside.

The compressor fan may also be malfunctioning, which will prevent airflow. Go outside while the AC is running and inspect the fan to see if it is turning and note how fast it is turning.

If the fan is not rotating as it should be, this can cause hot air to blow through the system, and this can make copper pipes hot and cause warm air to blow into your home instead of cooling relief.

If the condenser coil inside the compressor is clogged, this will also prevent airflow that keeps the system from cooling properly. The coils are essential for cooling the air that goes into your blower, so a clog here will prevent the AC from working as it should.

Clean the compressor and clean around the compressor to remove any plant growth or debris that may be hampering air flow and functionality. You should also clean the coils, which means you will need to remove the housing around the outdoor AC unit in order to access them.

Turn the power to the air conditioner off completely before cleaning the compressor or the coils. Do this by flipping the circuit breaker that supplies power to the AC.

Once the housing is removed from the compressor, use a garden hose on a gentle spray to clear out grass clipping, twigs, dirt, and other debris that tends to build up inside the unit.

Let this dry for about 30 minutes to an hour before you turn the AC back on and see if this has solved the problem.


A blockage in the copper pipes could be causing the refrigerant to back up in the line. If something is stopping the coolant from flowing through the pipe, cooling air will not get pushed through the blower to cool down the interior.

This blockage will create hot pipes closer to the unit that disperses air into your home. To test for blockage, gently and carefully touch along the length of the copper pipe to see if you can find a spot that is cool.

If you find both a hot and a cool section of copper pipe, this indicates that there is a blockage in the pipe that is preventing the coolant from flowing. You will need to power off the system, disconnect the pipe where the clog is located and clean this out.

Reconnect the pipe, power the AC back on, and see if the problem is now solved.


Over time, copper pipes can wear out and break down and develop small leaks. Pinhole leaks are so tiny they are nearly impossible to see, which can make them very hard to detect.

Even tiny leaks will cause coolant to leak out of the system, and it can affect the pressure that drives the coolant through the pipes. This will result in a lack of cold air blowing out of the system.

To check for leaks, turn off the system completely. Fill a spray bottle with soapy water and spray this solution all over the pipe.

Look for little bubbles, which indicate there is a leak. If you find leaks, replace the damaged part of the pipe and see if this fixes the issue.

hands working on air conditioner

Air Conditioner Not Cooling

There are a few different problems that can keep your AC from getting cool. When the air is warm, and the copper pipe connected to the blower is also hot to the touch, this points to some very specific problems that you can troubleshoot and repair on your own.

Get more comfortable with the various parts of your air conditioning system and you will be more comfortable giving it regular maintenance.

This knowledge will even make it possible for you to perform minor repairs and fixes that can keep you feeling the cooling joy of a working AC.

AC Not Cooling FAQ

Why is my AC pipe not getting cold?

The pipe running to the interior AC unit should be cool to the touch, not hot. A hot pipe indicates that there is a problem with the compressor, which sends cooling refrigerant through the system, or that there is a blockage in the line.

If your copper pipe is hot and the air conditioner is not blowing cool air, you will need to troubleshoot the problem and fix it.

If you still aren’t getting cool air and the pipe is still hot after you have performed some basic maintenance and possible fixes, it’s time to consult with a professional HVAC specialist to further diagnose and solve the problem.

What is the small copper line from an air conditioner?

The small copper pipe connects the outdoor unit and the indoor unit in a split air conditioning system. The pipe conducts coolant from the compressor to the indoor unit that supplies cooling air inside.

If this copper pipe develops a blockage or a leak, the coolant will not reach the blower. This will result in warm air coming from the blower, rather than cool, and can make the copper pipe hot, too.

Does the AC pipe get hot?

If your AC unit has an exhaust pipe, this pipe may get hot. But the small pipes connecting the indoor and outdoor units of the air conditioning system should always be cool to the touch and will feel cool when the system is functioning correctly.

If this pipe is hot, something is not working the right way. Whatever is causing the pipe to get hot will also cause warm air to blow into your home, rather than the cool stuff you want.

What are the signs of an overcharged unit?

When an air conditioning system is "overcharged," that means it has too much refrigerant. And like with all things, too much is just as bad as too little.

When there is too much refrigerant, there will be more pressure in the condenser, and the air blowing inside from the unit might feel sticky or moist. Too much coolant can also cause subcooling, which makes the cool air far too cold.

This subcooling can cause freezing in the coils and along the copper pipe, which will impede air flow and may even cause the system to shut off. The AC won’t work again and will not provide cool air again until the frozen parts unthaw.

Will overcharged AC not cool?

An air conditioning unit that has been overcharged with coolant, meaning that it has been overfilled with refrigerant, will not cool as effectively. The airflow may be weak and even warm.

The excess of coolant makes everything work harder and run hotter. It will even make the air conditioner consume more energy.

Too much of a good thing is way too much of a good thing in this case. An air conditioning system that has received too much refrigerant can cause damage to the compressor and other mechanical parts in the system.

Further Reading

Home Air Conditioning Compressor Replacement

How to Clean Your Air Conditioner at Home

How Humidity Affects Air Conditioning Efficiency

How to Install an Air Conditioner Fan

Replacing Freon in an Air Conditioner

Troubleshooting Common Air Conditioner Blower Problems