AC Compressor Ultimate Guide: Types, Maintenance, Common Problem, Cost

This comprehensive guide provides full details about AC compressor types, how to keep them running efficiently and AC compressor costs should yours need to be replaced.

AC compressor cost details are found below, but some readers are here for that information only, so let’s talk about air conditioner compressor prices for a second.

AC compressor replacement cost is $1,250 to $2,500 for most residential units, according to the PickHVAC AC Repair Guide that includes replacement costs for a full range of AC parts. These costs are for residential, split system and mini split air conditioner systems. Commercial compressor replacement costs multiple times more. We’ll explore that below in the Cost section.

OK, let’s get into the details. Feel free to use this Navigation List to jump to topics of interest, if desired.

Note: In this guide, we call the outdoor unit the “condenser unit” and the “condensing unit.” The terms are interchangeable.

What is an AC Compressor?

The compressor in your air conditioner or heat pump is the “heart” of the unit. It is the part that pumps refrigerant, aka Freon, through the system. By the way, Freon is a brand name. But it is commonly used of any type of refrigerant, like Kleenex or Ketchup.

AC Compressor

AC Compressor

Your AC or heat pump system has an indoor coil, outdoor coil and a set of lines connecting the two. The compressor is the piece of equipment that cycles refrigerant from coil to coil through the line set. It is located in the outdoor unit, which is technically called the condensing unit. For more details, see our 5000-word AC Condenser Unit Guide. It’s just as comprehensive as this AC compressor guide.

How Does an AC Compressor Work?

To understand how an AC compressor works, we should start with a deeper discussion of the major components in your heat pump or AC system.

How Does AC Work

1). Refrigerant is an amazing substance – life-saving, really, since air conditioning has saved countless lives in the last century. Refrigerant evaporates very easily, becoming a low-pressure gas. As refrigerant evaporates, it collects heat – just like when wet skin feels cool in the breeze. That’s water evaporating, taking away heat, and making you cooler.

The refrigerant can also be compressed from a high-pressure vapor back into a low-pressure substance – but that’s getting ahead of ourselves.

2). Evaporator Coil: Inside your home, in the furnace or air handler, is a radiator-like coil. There are several designs, but many are A-shaped with sloping sides.

As the refrigerant enters the evaporator coil, it evaporates, of course, into a low-pressure gas. As it does that, it collects surrounding heat to carry from your home – and the air in your home gets cooler. That chilled air is pushed into your ductwork by the blower motor, and the blower also pulls in warm air to be cooled.

As a side note, the evaporator coil gets really cold, and moisture from the air condenses on it. The water runs down the slope of the A-coil, and is drained away. AC makes the air in your home cooler and drier, and dry air is more comfortable than damp air.

3). Refrigerant line set: The lines running between coils are often copper, but synthetic materials are used in some AC types. One line carries refrigerant vapor from the evaporator coil to the condensing coil outside. The other line carries cooled refrigerant from the condenser unit to the indoor/evaporator coil.

4). The Condensing unit outside contains the compressor. This is where our discussion gets to the topic at hand. The compressor has one hugely important purpose – it compresses the high-pressure gas vapor back into a low-pressure gas. This does two things. First, as the refrigerant vapor is compressed, its temperature rises – the same amount of heat in less “space” makes it hotter. It gets so hot that the outside air, even on a hot summer day, is cooler than the refrigerant. That is essential for heat to leave the refrigerant, since heat likes to balance out, flowing from hotter to cooler space. The heat is transferred through the outdoor coil, which is also radiator-like. It has fins to maximize surface area for fast heat transfer to outside air.

Secondly, and here is the answer to the question at hand, the compressor compresses the refrigerant. This raises the pressure of the refrigerant. From physics, we understand that substances flow from a place of high pressure toward lower pressure. It is that change in pressure that causes refrigerant to flow through the system – from high pressure in the outdoor unit to low pressure in the indoor unit. Inside, the refrigerant collects more heat to carry outside. The cycle is continuous when an air conditioning cycle is in process.

Types of Air Conditioner Compressors

This guide discusses the five AC compressor types.

Scroll, rotary and reciprocating AC compressors are the most common types used in residential air conditioners.

They are also used in commercial ACs along with screw compressors and centrifugal compressors.

Here is an overview of AC compressor types.

Scroll Compressors

AC Compressor scroll compressor

Scroll compressors are among the most popular AC compressor types. They are typically used to replace other styles when those other compressors fail.

The Copeland UltraTech Scroll compressor is considered by HVAC technicians to be the finest of its kind.

How does a scroll compressor work?

Two identical spirals make up the core of a scroll compressor. One spiral is fixed, that is, stationary. The second spiral moves in sort of a wobble or vibration, driven by an offset crank. It “floats,” meaning it is free to move. As the moving spiral rotates, it compresses the refrigerant into a high-pressure vapor.

The vapor is forced toward the center of the compressor, becoming denser, more compressed as it travels. In the center, it leaves the compressor for circulation through the system. Pneumatic Tips offers more details for those that enjoy technology.

Benefits of a Scroll Compressor

Scroll compressors have many benefits.

1). They are efficient. Replacing an old reciprocating compressor with a scroll compressor will boost efficiency and save you money.

2). They are reliable. Many companies cover their scroll compressors with a 20-year or Lifetime warranty. That shows the manufacturers have confidence in their products.

3). They don’t fail if liquid, such as water, gets into the refrigerant. The problem with liquid is that it cannot be compressed. The movement of the floating spiral allows for moisture to travel through the compressor without causing failure. Make no mistake – moisture in the refrigerant is not a good thing. That’s why ACs are equipped with parts called filter driers to remove moisture from the refrigerant.

Liquid in the refrigerant lines of a unit with a reciprocating or other type compressor will damage it because there is no wiggle room.  

4). They don’t have valves. In other compressor types, valves allowing refrigerant in and out eventually wear out. Instead, the scrolls tend to get more efficient with time.

5). Single-stage (1-stage) and 2-stage scroll compressors are available. A 1-stage unit runs at full capacity whenever on. They are more affordable but not as efficient – fine for areas with moderate and cool summers.

A 2-stage scroll compressor operates on low or high, depending on whether the low stage can keep up with cooling demand. If not, it kicks into high, meaning it cycles the refrigerant more quickly.

Rotary Compressors

Rotary compressors are the compressor of choice for mini split ACs and heat pumps, also called ductless ACs and heat pumps.

Some standard split system air conditioners and heat pumps, such as top models from Daikin, use rotary technology.

How does a rotary compressor work?

Cylindrical in shape, rotary compressors do have suction and discharge ports connected to the refrigerant lines, so they are different from scroll compressors in this regard. Refrigerant enters a rotary compressor through the suction line and exits through the discharge line.

Within the cylinder, aka compressor shell, a roller is connected to the motor shaft and spins at the same rate as the motor. The diameter of the roller is less than that of the cylinder. As the roller rotates, the offset crank causes it to contact the inside surface of the cylinder as it goes around. In doing this, refrigerant vapor is trapped against the side and compressed.

A spring-loaded vane is forced against the roller side preventing compressed refrigerant gas vapor from escaping – ensuring that it is compressed. The pressure of the gas will exceed the pressure in the discharge line, and the vapor will be discharged to cycle back to the evaporator coil. The suction valve opens, and more refrigerant enters. This is a continuous cycle too.

Benefits of a Rotary Compressor

There are a couple things worth noting.

1). These units are among the most efficient compressors, often reducing energy use by 25% or more compared with other types. The reason is that they maintain near-perfect balance in temperature by speeding up or slowing down to circulate exactly the right amount of refrigerant to meet the air conditioning demand.

2). Indoor comfort is optimized as an ancillary to efficiency.

3). They are very quiet. The noise level of a rotary compressor is in the 40-55 decibel range while the noise level of scroll compressors and other types is in the mid-60s to mid-70s for residential air conditioners.

Reciprocating Compressors

These are an older style compressor. They were commonly used with R22 refrigerant. However, since R22 is being phased out, these compressors are less common than rotary and scroll compressors.

Reciprocating means that the mechanics in the compressor – pistons – moves back and forth within a cylinder. They’re also called piston compressors and positive-displacement compressors.

On the low-pressure side, refrigerant gas enters the suction manifold. The piston moving up and down, driven by a crankshaft, compresses the gas before it is discharged. Valves on each side open and close based on the pressure within the compressor.

The upward motion of the piston closes the suction valve, and vapor is trapped in the compressor. As it is compressed, its pressure becomes greater than the pressure in the discharge line, and the discharge valve is forced open to discharge the vapor. This pulls more vapor in through the suction line and valve.

Benefits of a Reciprocating Compressor

The main benefits are that the design is fairly simple, and performance is reliable. Reciprocating compressors are also available in many sizes, so can be used in both residential units up to 5 tons and in larger commercial air conditioners.

Screw Compressors

These are large commercial compressors also called rotary screw compressors. The system employs two rotating helical screws that interlock. Gas vapor moves in from the suction side, and the action of the screws compress the vapor and move it along from the large end to the small end.

The internal pressure becomes greater than the pressure in the discharge line, the valve opens, and the vapor is discharged, as in other compressor types. Additional refrigerant gas enters the suction side, and the process continues.

Benefits of a Screw Compressor

The primary benefits are simple design and reliability plus their large size. Most Rotary screw compressors are 10 to 20 tons in size and used in commercial applications.

Centrifugal Compressors

These units draw refrigerant into their compressor using a piston and cylinder. A rotary impeller driven by a crankshaft turns, causing the refrigerant to spin at high speed. This compresses the refrigerant in the cylinder before discharging it and pulling in more from the suction side.

Benefits of a Centrifugal Compressor

Also called radical compressors, they are typically used in large installations, though not suitable for residential use. They are energy efficient and cheaper to build than other commercial type compressors. Centrifugal compressors also produce higher constant airflow than other commercial types like a reciprocating compressor.

How to Maintain an AC Compressor & Why you Should

All compressor types must be maintained to keep them running as efficiently as possible and to prevent mechanical breakdowns. Keep in mind that a heat pump is exactly like an AC, but it can reverse the process by capturing heat outdoors in winter and dumping it inside.

We mention this because the compressors in heat pumps are identical to those in air conditioners, so your heat pump compressor needs the same maintenance.

Here are the essentials of compressor maintenance.

1). Check seals on both suction and discharge lines. If there are leaks, replace the seals. The seals might also be preemptively replaced during annual maintenance.

2). Clean the coils in both indoor and outdoor units. A dirty coil reduces heat transfer. That causes the compressor to work harder than normal to cool the air. The results are lower efficiency and potential mechanical failure. According to Carrier, this is a two-step process. First, vacuum large debris from the coil fins. Then clean the fins using a coil cleaner. Spray it on, let it sit for the time recommended on the container, and then hose it off. You might be surprised how much dirt comes off and how much cleaner your coil looks afterward.

3). Change the air filter in the air handler as needed. A dirty filter will prevent airflow, and the air conditioner will work harder than necessary, reducing effectiveness and efficiency.

4). Also clean the louvers on the condenser unit jacket. There’s a theme here. Leaves, dust and debris prevent airflow and cause the unit to work too hard.

5). Check the refrigerant level annually. Low refrigerant means there is a leak. An AC low on refrigerant will not cool effectively. This must be done by an HVAC technician with the appropriate testing gauge.

6). Wrap the condenser unit in an insulated blanket during winter if your climate experiences extreme cold.

7). In summer, flip the high pressure switch, if your unit has a toggle switch for this purpose. It might also have a low-pressure switch that should be activated. These switches are automatic on most split system air conditioners being manufactured today. The pressure switches prevent the AC from running when refrigerant pressure is too high or too low. Both situations will harm the compressor.

8). Shield the condenser unit from direct sunlight, which will heat up the compressor and coil and make discharging heat more difficult. Use of a 4x8 sheet of plywood or OSB is common, but make sure it isn’t placed so close to the unit that it blocks airflow.

9). Trim bushes, shrubs or overhanging tree branches that might block airflow into the condenser. These branches might also grow into the fan cabinet and damage the fan when it comes on.

Reasons For AC Maintenance

Why should you get regular AC compressor maintenance? We can think of four reasons.

First, so your AC compressor will run as durablyas possible.

Secondly, to maintain the best efficiency. If a 16 SEER air conditioning system has dirty coils or filter or other issues commonly solved with maintenance, efficiency will drop. It could be as low as 12 or 13 SEER, a 25% to 33% drop, meaning higher energy use and costs.

Thirdly, most air conditioner warranties make it the homeowners responsibility to have annual maintenance done on their condensing unit – the entire HVAC system, in fact. Here is just one example of an AC warranty from a common brand. It’s written in very similar language to what you’ll find in the AC warranty of almost any brand.

Allied Air (Armstrong Air and AirEase brands) says, Your new Allied Air unit must be properly installed, operated and maintained in accordance with the unit installation, operation and maintenance instructions provided with each Allied Air unit. Failure to provide maintenance per Allied Air instructions will void this warranty. Meaning, if you don’t have it properly installed and maintained, warranty claims could be denied. Allied Air’s warranty also states that in your warranty claim, you must provide, “Proof of required periodic maintenance, installation date and location.”

Most brands require annual maintenance. Again, this isn’t just an Allied Air thing. They’re all about the same.

Heil’s warranty puts it bluntly too, “Proof must be supplied that the equipment has been properly maintained over the life of the warranty, i.e., a minimum of once-a-year maintenance.” They don’t sound very forgiving, do they?

Fourthly, even if the unit is under warranty and the repair company overlooks the fact it wasn’t maintained – in other words, they’ll file a claim on your behalf anyway – you’ll still get a big bill. Why? Because labor isn’t covered on most air conditioners from Day 1. A few brands (see the Warranty section below) offer labor coverage for one to three years, which is almost never used. Most do not. The labor cost to switch out a compressor will run to $400 or more on most units. See our HVAC Warranty Guide for detailed information about warranties

Common AC Compressor Problems

The good news is that AC compressors are pretty durable. Because they are the heart of the condensing unit and so expensive, manufacturers can’t afford to put “junk” in their units. Their reputations would be harmed quickly.

The bad news is that when a compressor does go bad, it often spells the end of the life for the entire unit since replacement is so expensive.

OK, with the good news/bad news out of the way, here are common AC compressor problems.

Circulation Problems

When warm air is coming out of the grates – or “room temperature” air, then the air isn’t being cooled. This is usually because refrigerant isn’t circulating into the indoor coil, capturing heat, and taking it outside. Check to see if the system has been accidentally turned to Heat or Fan modes.

If it’s on AC and you’re not getting cool air, it could be a compressor problem or a refrigerant leak. Another cause of compressor circulation problems is a blocked or damaged refrigerant line. This is rare, but if a tree branch fell on the line, someone ran into it with the mower or similar issue occurred, the line could be crushed or crimped and prevent refrigerant circulation.

Working Too Hard / Overheating

In the maintenance section above, we emphasized the need to keep coils, louvers and other key components clean of dirt and debris. And keep the filter in the air handler changed. A failure to do these steps will result in the AC compressor having to work “overtime” to remove warm air from your home.  

Hard Starting, Ticking or Clanking

Does the compressor make excessive sputtering or clanking noises when it comes on – or as it continues to run? This is often caused by an electrical issue such as faulty/worn/chewed wiring or a failing AC capacitor or relay.

Refrigerant Pressure Problems

Discharge pressure that is too high or too low will result in lost cooling capacity. If your unit has pressure gauges – only a few do – then check the pressures against what the manual says they should be. If the pressure is off, call an HVAC technician for an AC compressor troubleshoot.

Burned Out AC Compressor

If the unit doesn’t make any cool air, the compressor might be shot. Have someone adjust the thermostat while you stand outside next to the condenser unit. If nothing happens, or if it makes unusual noises, it could well be a failed compressor. Again, an HVAC technician can check it out and diagnose it quickly.

Bad Compressor Repair

Did you know that many HVAC problems including AC problems are the result of improper repairs?

Really good HVAC technicians will tell you that they spend a lot of time fixing other people’s bad repair jobs. If you have your condenser unit worked on in the last year or so, and it isn’t working properly, the repair might have been done wrong.

One common bad repair issue is installing a suction line that is too small. This could happen during initial installation or when replacing a damage line. A line that is too small will cause overworking by the compressor and eventually ruin it.

Overcharging Refrigerant

Too much AC refrigerant isn’t good either. The pressure can easily damage the compressor. As we’ve explained, if your AC starts acting up shortly after it has been installed or repaired, it’s likely somebody messed up your AC system. All AC repairs should come with a warranty of at least 30 days.

We recommend calling the company that made the repair. Try to get them to agree over the phone that if something was done improperly, they will cover the cost of labor and parts to repair it. If they won’t, you will likely have a better result contacting a different company and paying for the new repair. Sure, it’s costly, but so is letting a bad technician have another chance to damage your compressor or other HVAC component.

Refrigerant Contaminants

Your AC system has a part called a filter drier. It is designed to remove moisture from the refrigerant, so that the refrigerant can be properly compressed. When moisture or another contaminant such as dirt gets into the refrigerant, which isn’t common, and past the filter, it can cause problems for the compressor. The most common time for dirt and debris to get into the refrigerant is when the filter is being installed or replaced. Make sure to hire an experienced technician for the job.

Note: Some techs install the filter drier outdoors near the condenser unit. A better option – the proper option – is to install it indoors near the indoor coil. It will last much longer not being exposed to the elements.

The Circuit Keeps Tripping

If the electrical circuit for the condenser unit keeps tripping, it could be caused by a bad compressor or an electrical issue, which would likely be a cheaper fix than compressor replacement. If the breaker/circuit keeps tripping, have the system inspected for the cause.

How to Know your Compressor is Bad

We’ve just covered common AC compressor problems.

This section summarizes the symptoms and how to know your compressor is bad.

  • The condenser unit is dead – the AC is turned on, the thermostat is calling for air conditioning, but nothing is happening. Make sure the circuit is ON. If it is, and nothing is happening, it might be the compressor.
  • The condenser unit is running, but the air isn’t being cooled. Sure, this could be a refrigerant leak or electrical problem, but the compressor is a prime suspect too.
  • The condenser unit/compressor is making terrible noises, like something is broken or loose.

How to Replace an AC Compressor

This is not a DIY job for most of us for one simple reason – you need to have a “refrigerant card” to buy refrigerant to charge the system, meaning you must be certified in the handling of refrigerants. 

However, for those who want to know the basics, here is an overview, sort of a short step-by-step AC compressor guide without much detail.

In preparation of the job, take several pictures of the old compressor from various angles to show where the lines and wiring connect. Take them with you to purchase the new compressor. The job will go easiest when the new compressor is as much like the old as possible.

1). Turn off power to the unit including pulling the disconnect from the box near the condensing unit outside. Inside the unit, pull the wiring harness out of the compressor. Go slow – firm but gentle – to avoid damaging the wiring and creating hassle for yourself.

2). Remove the fan top by removing the screws or bolts and lifting it up and off the unit.

3). Clean all flammable debris out of the inside of the condensing unit, so there is nothing in there that can catch fire.

4). Recover refrigerant in the system. This takes special equipment and is covered in this video.

5). Remove the valves on the high-pressure and low-pressure sides.

6). Protect the king valve refrigerant connections and wiring with a damp cloth or a heat barrier spray like Cool Gel. Or do both. You’ll see why in the next steps.

7). Remove the bolts holding the compressor in place in the condensing unit. You might need a wrench extension to reach the bolts.

8). Fire up a torch, and heat up the lines within an inch or two of there they connect to the old compressor. This melts the solder out of the connections, so they can be separated. Another option is to cut the connections with a pipe cutter. In fact, that’s the technique preferred by most experienced technicians.

9). Once the refrigerant lines are removed, pull the old compressor out of the unit.

10). Use sandpaper designed for metal to clean up the copper pipes. Using 120-180 grit is recommended. Wipe where you’ve sanded to remove remaining grit.

11). Use a wet rag or heat barrier to prepare for sweating in the connections.

12). Keep your new compressor upright. Install the rubber feet and metal inserts into them. Lift the compressor, and set it in place, and install the bolts holding it to the condensing unit.

13). Press the refrigerant lines back into place in the new compressor.

14). Use the torch to heat the connections, running the torch back and forth rather than focusing it on any spot. When the connections are hot, apply solder to hold them tight.

15). Run nitrogen through the system (again, special equipment needed) to purge the system to ready it for refrigerant.

16). Reconnect the electrical harness.

17). Apply the vacuum to the system for 30 minutes, and leave on vacuum pressure for 30-60 minutes. Use your meters as monitoring gauges to ensure that there isn’t a leak in the system.

18).  Charge the system with refrigerant.

This video covers all the above steps.

When replacing a compressor, also consider replacing the capacitor, Schrader valves and other small components often considered “normal maintenance” items on an older AC.

AC Compressor Warranties – What’s Covered?

HVAC warranties including compressor warranties have become more competitive in the last few years. Brands are offering longer warranties, in other words.

However, we should stress again that if you don’t keep your condenser unit maintained, the warranty might be considered void by the HVAC manufacturer when the repair contractor makes a claim. See the section above called How to Maintain and AC Compressor & Why you Should for 4 compelling reasons.

Lifetime

Goodman has offered Lifetime warranties on compressors for decades. Since Daikin bought Goodman, the warranties top to bottom in the AC lineup aren’t quite as good, but they are still the best in the industry. Goodman offers the Lifetime warranties on its two best models.

Amana is a sister brand to Goodman, and it offers a Lifetime warranty on its four top models. Amana takes it a step further with a Unit Replacement warranty – if the compressor fails, Amana will replace the entire condensing unit. Goodman used to offer these, but doesn’t now because of the lower price of Goodman vs Amana ACs. Instead, Goodman will replace the entire unit if the compressor fails in the first 10 years.

Twelve / 12 Years

Trane and American Standard’s best models are covered with a 12 year compressor warranty. All other Trane and American Standard models are backed by 10-year compressor warranties.

Ten / 10 Years

A 10 year compressor warranty is the industry standard. Brands offering a 10 year warranty on some or all models include Trane, American Standard, Carrier, Bryant, Lennox, Rheem, Ruud, Armstrong Air and Heil.

One of the nice things about the Carrier and Bryant units are that all have 10-year compressor warranties, even the most affordable models.

Five / 5 Years

We don’t see many of these anymore. The cheaper Lennox Merit Series units are covered with a 5-year compressor warranty. That’s about the only units from “name brand” companies.

Some reviews recommend steering clear of a 5-year warranty. But it really depends on your needs. A cheap Lennox AC or similar is a good fit for cool climates where the AC doesn’t run heavily, in part-time homes like a vacation home, or when you’re planning to move in a few years.

Unit Replacement Warranties

This type of warranty provides for replacing the entire condensing unit if the compressor fails during the warranty period. It isn’t just the compressor that is replace. 

Goodman was the first to offer these, but now other brands do too. The ICP brands – Heil, Day & Night, Tempstar and others offer 10-year, 5-year, 3-year and 1-year Unit Replacement warranties on compressors along with a 10-year general parts warranty.

Daikin has 12-year Unit Replacement on its best models, and 6-year versions on mid-tier units.

Rheem and Ruud also offer 10-year Unit Replacement warranties on their two best central air conditioners.

AC Compressor Cost – Retail & Installed

As we noted, compressor replacement costs $1,250 to $2,500 for most models. Variable capacity compressor replacement costs as much as $3,300. That’s the part plus installation labor charges.

This table shows AC compressor cost by size, quality and with both retail and installed prices.

BTUs

Average

Premium

Installed

12,000-15,000

$685

$850

$1,250 - $1,600

18,000-24,000

$715

$945

$1,300 - $1,850

32,000-36,000

$780

$1,050

$1,445 - $2,125

42,000-48,000

$900

$1,135

$1,650 - $2,280

60,000

$1,150

$1,485

$1,870 - $2,500

Cost factors include:

  • Size of the compressor – Since ACs range from about 18,000 to 60,000 BTUs for split systems, cost rises with the size of the compressor needed.
  • Quality – Not all are created equal. Copeland is a premium brand, for example, at top cost.
  • Stages – Single-stage compressors cost less than 2-stage compressors. Variable capacity compressors cost the most. 
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