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AC Compressor Not Working: What’s Going On?

AC Compressor Not Working

It’s a hot day, and you’ve just returned home after a long afternoon out in the grueling Texas heat. The first thing you probably want to do is plop yourself down on the living room sofa and enjoy a refreshing rush of cold air. Except that today, of all days, you realize that something seems to be wrong with your air conditioner. How could this be? You hear the machine powering on and the familiar sound of air whirring through the system. Maybe it’s because of your AC compressor not working or another component that’s broken. Perhaps it’s another problem entirely.

Understanding how HVAC systems work can help you diagnose the problem you are having and determine what to do next. In this blog post, we’ll explain some of the common air conditioner problems, including why your air conditioner compressor might be turning on, but not cooling, and why an important part of your system could be working one minute and then stopping suddenly.

AC Compressor Working But Not Cooling

AC Compressor Working But Not Cooling: Common Culprits

Before we get into all the reasons your compressor might be playing a part in your air conditioner not working properly, let’s review what exactly this part does and why it’s important to cool your home’s indoor air.

Your AC actually operates using many of the same principles of your refrigerator. Your air conditioning system uses a cold indoor coil, which is your evaporator, to bring your indoor temperature to the desired level. Your condenser provides an outlet for the collected heat to be released outside through a hot outdoor coil. Both the evaporator and condenser coils are usually made of copper and are surrounded by aluminum fins.

The compressor serves as a pump, moving refrigerant between the evaporator and condenser. Your home becomes cooler when the liquid refrigerant passes through the evaporator and pulls the heat out of the air inside your home. This cool air is then circulated through your home through supply ducts and registers. The refrigerant, now a gas, then moves through the condenser, where it turns back into a liquid as it releases heat into the outside air. The evaporator, condenser and compressor are all located inside a metal unit, which is typically on top of a concrete slab next to your home’s foundation. Your AC compressor should last sometime between 10 to 15 years.

Now that we have gone over the basics, let’s talk about a few of the reasons your AC compressor might be working, but not cooling.

Pressure Imbalance

If the discharge pressure on your compressor is either too high or too low, your system could be underperforming. The pressure gauges on your unit can indicate whether this is your issue. If you aren’t sure where these are or what readings are normal, consult your manual. If you determine incorrect pressure may be why your AC is not performing, you’ll probably need to call in a technician to correct a pressure imbalance.

Loose Or Worn Gauge Ports

Another reason your AC could be struggling is if regular wear and tear has resulted in your gauge ports becoming worn or loose. In some cases, these can be tightened, while in others, you’ll need to replace these parts entirely.

Worn Thermostat Contacts

Over time, the electrical contacts inside of your thermostat can burn out, which can cause your fan motor to run, but not the compressor.

Your cooling and heating system has many parts, several of which can be responsible for an AC issue. We’ve covered just a few of the possibilities with the compressor in particular, but other components could also be contributing to your air conditioner underperforming or not working at all.

Air Conditioner Compressor Problems

Air Conditioner Compressor Problems: What Else Might Be Wrong?

In some cases, what you might think is a problem with your compressor is something else entirely. Check all your control settings and make sure nothing is different than what is outlined in your system’s instruction manual. Next, take a look at your air filter, ducts and your blower fan. A clogged filter is at the root of many air conditioning problems, so if you haven’t changed or cleaned your filter in a few months, performing this simple maintenance task can help your entire system run more smoothly.

If your air conditioner is not cooling your home to your satisfaction, you may need to check to make sure nothing is obstructing the airflow. If you have no air coming out of your vents, your blower fan might not be working correctly, your refrigerant line may have a kink or your air handler could be hiding a dirty filter or icy coils. You could also have a blockage in your condensate drain or even a coolant problem.

Sometimes a problem with your AC compressor can be linked to a broken condenser fan. If enough debris collects in your unit, causing your fan to become overworked and break, then the refrigerant cannot move from the compressor to the condenser and the indoor air circulating through your home does not reach your desired cooler temperature.

Similar to having a dirty air conditioning unit, your AC compressor cannot properly work if there are dirty coils within the system. Dirt, dust and other materials built up along the condenser coil, preventing the air conditioner from discharging enough heat from the system. This debris confuses your machine and causes it to repeatedly attempt to cool your space, leading to your compressor to overheat from the mounting pressure.

While it’s easy to recognize that there is a problem with your AC, and you might even be able to determine your compressor is the problem, most homeowners aren’t able to easily spot any irregularities in all of these parts. so you’ll probably need to enlist a professional to help you pinpoint exactly which component is to blame for your AC troubles.

The best way to prevent all of these possible problems is to schedule routine diagnostic tests with a licensed HVAC specialist. These visits can serve as an early warning system for potential problems, and help pinpoint exactly what parts are not working properly so that needed repairs can be made before your unit stops working completely. An experienced technician will:

  • check your unit’s refrigerant level
  • test for refrigerant leaks
  • safely remove any excess refrigerant in your system
  • look for any leaking ducts and close any gaps, as needed
  • calculate the airflow through your evaporator coil
  • evaluate your electric control system to make sure your heating and cooling systems will not operate at the same time
  • clean your electric terminals, and tighten connections, when necessary
  • apply oil to motors
  • inspect belts for damage
  • ensure your thermostat is accurate

Air Conditioner Compressor Not Turning On

Why Your Air Conditioner Compressor Is Not Turning On Entirely

When your compressor does not turn on, your system cannot circulate cool air. Why is that? The compressor moves refrigerant through the system by placing this substance under extremely high pressure and passing it on to the condenser so the refrigerant gas can morph into a liquid. First, make sure the unit is receiving power. You never know when a fuse has been blown, or a breaker has tripped within the unit’s system. You can see if the compressor itself is on by looking to make sure the switch in the outdoor compressor is on and that the 240-volt disconnect, which is usually located inside a metal box, is not shut off.

If you are sure the system’s power source isn’t why your compressor is not turning on, there are a few other reasons that your compressor might not turn on.

Your High-Pressure Switch Tripped

On a brutally hot Austin day, your compressor may stop working if your system detects that your outdoor motor has stopped working, or you have a dirty or obstructed condenser coil. In these situations, your high-pressure switch will turn your entire system off. You can usually reset the switch by pushing on the button which is in the compressor’s access panel.

Burned Out Compressor

An electrical problem can lead to a short or burn in the area between your compressor and the motor. In these cases, your unit won’t turn on at all. You can prevent these problems by having your system regularly inspected by a trained professional.

Malfunctioning Motor

If the circuits leading to your compressor become overloaded, you may need to reset the motor. To do so, look for the motor’s reset button, which pops out when there is an electrical fault. Wait until this part has cooled down enough that you can push the button in again.

Capacitor Or Contactor Problems

Your air conditioner will not turn on if your run capacitor is not working properly, since this part starts the fan and the condenser. The contactor works as a switch that controls both the compressor and the motor of the condenser fan. If you hear your air conditioner clicking, but it doesn’t turn on, you may have dirt or bugs that are causing this key part to fail, which in turn impacts the entire AC system. Checking and replacing both of these parts involves dealing with electricity and therefore is best handled by a professional.

An Old Evaporator Coil

Some problems begin when your system is first installed. If you have an older system replaced, or replace malfunctioning parts, you’ll want to make sure to put in a new evaporator coil that works with the condenser coil in the new condensing unit. If these two parts don’t match exactly, your compressor may stop working.

Your Compressor Has Reached The End Of Its Service Life

If you have an older AC unit, your compressor might need to be replaced. That said, many other problems can be blamed on the compressor, so making sure the problem is not with your overlaod protector or your capacitator before getting a new compressor. If you do decide to get a new compressor, have a licensed technician perform the installation.

While you can replace just the compressor, many homeowners elect to install an entirely new air conditioner. When you consider the cost savings that come with making that investment, you will probably save money over the long run. The most efficient models today, even when compared to systems that are just 10 years old, can reduce your energy costs by 20% to 40%.

Air Conditioner Compressor Starts Then Stops

Air Conditioner Compressor Starts Then Stops

Sometimes your compressor will stop working, then start again. In many cases, this is because your system is bigger than your home needs. Although it may seem counterintuitive, buying a large air conditioner not only costs more, but also is less efficient. Having your air conditioner cycle on and off leads to larger differences in indoor air temperatures, which is ultimately less comfortable for you and your loved ones. This frequent cycling also makes it harder for your system to reduce moisture in the air, increasing indoor humidity. Last, and perhaps most important, is that if your AC is coming on and off repeatedly, your components are working harder than they are designed to do, which can cause both the compressor and the fan controls to wear out. The size of your AC system should be based on how big your home is, how many windows you have, how much shade your house gets, how much insulation you have, how much air makes it inside from outside of your home and the amount of heat produced by the people and appliances in your home.

If your unit is hard starting, you may also have something going on with your fuses and wiring. In these cases, you may need to have a fuse replaced and wires repaired. Yet another related common problem is when terminals and wires become corroded. If you are having regular maintenance done, your technician should be checking for these types of issues, which can cause your AC to work sporadically.

ABC Can Keep Your Home Comfortable

As you can see, air conditioner problems can stem from an almost mind-boggling number of causes. You can easily spend your entire weekend trying to troubleshoot a problem with your compressor or one of the other components that work together to cool your indoor air. ABC Home & Commercial Services has been handling Central Texans’ AC woes for generations. Our team of skilled technicians understands exactly how your air conditioner works and can quickly get that gloriously cool and refreshing air blowing in your household once again. With ABC’s help, you can have your air conditioner regularly serviced, repairs handled and even a new unit installed, all with the confidence that comes from trusting in a company with a proven track record and friendly, reliable service.

Tom Riggs

Tom Riggs is the Division Manager for Mechanical Services, overseeing sales and operations for HVAC, Plumbing, Electrical, Appliance Repair and Water Quality for all ABC Austin branches. He joined ABC in 2014. Before ABC, he was an HVAC Service Technician, HVAC Comfort Advisor/Sales and Operations Manager. Tom attended Universal Technical Institute. He's an avid outdoorsman and enjoys country living with his wife and two sons.

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