How To Fix It

What are HVAC Most Common Failures?

When your HVAC unit starts to show signs of wear or failure, it can be a headache to diagnose. With all the parts involved in operation, there could be several points of failure on a system.

Having an understanding of the common failures of an HVAC system can help you determine what will be needed to be fixed.

When in doubt, always refer to a professional for help. While the owner can accomplish basic maintenance, serious problems should be handled by someone with an HVAC license. Proper care is the best way to prevent failures. That being said, here are some of the most common HVAC failures.

Refrigerant Leak

A refrigerant leak can cause your system to not perform as usual. A reduction of refrigerant over time is not part of the regular operation of your system.

Too much loss causes poor performance. In a healthy system, you will see the same amount of refrigerant circulated continuously.

It is not like the oil in an automobile, which needs topping off and replacement. 

If your system is experiencing a refrigerant leak, be on the lookout for:

  • Your registers are not blowing cool air – Check your vents; if the air is not as cool as it should be, that could be a sign your refrigerant is not at proper levels.
  • Icy evaporator coils – When refrigerant is leaking, your coils can’t maintain the proper temperature, and they start to freeze over.
  • Subpar cooling – Refrigerant is essential to proper cooling. If your space is not cooling as fast as normal, this can indicate a leak.
  • Hissing Sound – Since the leak is probably coming from a crack or hole, you may be able to hear a distinct hissing or gurgling sound from the area.

While these symptoms are not exclusive to a refrigerant leak, it is an excellent place to start if you are experiencing them. 

Fixing a refrigerant leak may need the involvement of an HVAC professional. You may be able to find temporary stop-gap measures to fill the leaks, but they may not last. It is tempting just to keep refilling the missing refrigerant.

While this can solve the problem, the fluid will always leak out and need another top off. This can be costly in the long run.

Faulty Fuse or Breaker

These safety devices help prevent your unit from causing electrical damage. When your HVAC system is drawing too much power, a fuse may blow, or a breaker might trip. It can be annoying to deal with, but it is better than trying to handle an electrical fire. 

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Fortunately, a tripped breaker can be an easy fix. If you have an older home with fuses, it may be a different story. In contrast, a fuse will need to be replaced. 

Tripping a breaker or blowing a fuse is usually a sign of another issue. HVAC systems are relatively complicated, and one symptom can be the sign of several issues.

Keep in mind that when it comes to tripped breakers and blown fuses, diagnosing the problem could lead to another issue. 

Here are some of the reasons why you might trip a breaker:

  • Bad AC capacitor
  • Dirty Air filters
  • Dirty coils
  • Low refrigerant levels
  • Mini-split systems

Damaged Parts

If you are using your HVAC system a lot, you could be causing premature failure. This can be the case if you live in a hotter climate and need to run your system frequently.

Sometimes, old parts can be the culprit. At around five years or so or regular use, parts start to wear and break. 

Some common parts wear down most often. They usually are the ones that get the most use when your system is operating.

They are:

  • Fan Blades
  • Compressor
  • Electrical Connections
  • Electrical Contacts

Being aware of what your system looks and sounds like when running well is a great way to catch damaged parts before they cause a severe problem.

Some parts are easier to replace than others, like a fan blade, and can be done by yourself. Other replacements are best left to professional HVAC servicers.

Frozen Coil

Frost coils are hard to miss. If your system is trying to keep up with the summer heat and you find your coils are covered in ice, it can be a clear sign there is an issue. 

If you think you may have a problem with your evaporator coils, there are some other signs to look out for:

  • Check for ice on the outside refrigerant line.
  • Inspect the air handler for condensation and water buildup.
  • If your condensation pan is full or overflowing, check to see if it’s a clogged drainpipe. If not, it may be your coils.

Once you have identified that the evaporator coils are causing issues, you can now track the problem’s source.

Several underlying problems can cause icy coils. Before you start to diagnose your coil issue, it is good practice to turn off the breaker that feeds power to the unit. This will give the coils time to defrost.

Common causes of icy coils:

  • Dirty evaporator coils – Your evaporator coils transfer refrigerant to the heat pump. If they are dirty and covered with grime, they will strain to try to accomplish this task.
  • Airflow problems – If your blower can’t operate properly, it can cause icy coils.
  • Low refrigerant – Low refrigerant causes strain on your system, sometimes producing ice on evaporator coils.
  • Poor Drainage – If your system is working in a humid climate, a blocked drain pipe can cause strain on your system.

Fault in Your Thermostat

When your system starts acting up, it can be easy to always go for the worst culprit. Whether you are worried about costly repairs or just stressed about your AC not cooling, make sure you check your thermostat.

While this piece of your system is often overlooked if it is not working or malfunctioning, it could cause a lot of the same issues we’ve explored before.

Here are a few symptoms of a faulty thermostat:

  • Subtle or sudden changes in your system’s performance.
  • Unit short cycling or running constantly.
  • Warmer environment relative to temperature settings.

A lot of these issues are similar to more serious problems. Before you decide, you need to call an HVAC specialist, check to see if your thermostat is in working order.

It’s easy to misinterpret system failures as urgent HVAC problems when a simple fix may be the solution.

Things to look for when inspecting a thermostat:

  • Is your thermostat receiving power?
  • Check the inner electrical components for wear, dirt, and grime.
  • Was your thermostat appropriately installed?
  • If your thermostat is mechanical, is it an issue with the heat anticipator?
  • Is your thermostat in an optimum location?

Dirty Filters

One of the easiest and often overlooked ways to prevent HVAC failures is to keep up with regular filter replacement.

The effects of a clogged or dirty air filter can cause some severe problems to your system over time.

Dirty hvac filters

An AC or heat pump needs proper airflow to push air across the coils or heat exchanger efficiently for proper operation.

Here are some issues caused by dirty filters:

  • Unit not working at all.
  • Clogged filters can cause your coils to freeze up.
  • Mechanical damage to your compressor or heat pump.

When your system is working with clogged filters, it can cause your coils to freeze up.

This means that the refrigerant is still running, but there is no air to flow over the coils, so cool air is staying put.

Frozen coils are a common issue with dirty filters but what homeowners don’t anticipate is that when they replace the air filter, the problem persists.

What happens is that the coils are so frozen that even with the extra airflow, they stay icy.

The only way to solve this problem is to allow the system to defrost. One thing that most people don’t anticipate is the water coming from the defrosted coils.

Depending on where your unit is located, this can cause some serious water damage.

Lack of Regular Maintenance

Much like your car, your HVAC system needs annual maintenance to run correctly. Soliciting the help of an HVAC professional can really be beneficial here.

They can diagnose problems before they become serious and more costly. It can even break your warranty if you fail to keep up with maintenance, so make sure you are taking care of it.

While an HVAC technician can take care of maintenance for you, there are still some things you can check yourself. 

Here is a quick list of recommended maintenance points to check:

  • Inspect refrigerant lines for leaks
  • Make sure your unit is free from debris that may impede mechanical performance.
  • Clear at least 2 feet of space from around your HVAC unit.
  • Replace air filter every 90 days
  • Lubricate the HVAC motor and check the fan belt
  • Make sure your AC unit is level to the ground.


Your HVAC is an important part of keeping your home comfortable. While we rely on these systems daily to heat and cool us, some common failures happen.

The best way to stop them from happening is to keep a regular maintenance schedule with yourself or with a licensed HVAC technician. To stop failures prevent them early.