Air Conditioner Compressor Application: A Home Owner's Guide

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Last updated: 
December 28, 2016

An air conditioner is a functional system composed of four mechanical parts: the compressor, the condenser, the evaporator, and the expansion valve. When the air conditioner compressor starts giving you headaches, it’s important to know how to deal with it.

The purpose of an air conditioner compressor is rather complexly worded. In essence, it works to transmute refrigerant compound from a gas state to a liquid state and then back to gas. The cycle is continuous and it manages to relieve the evaporator of the heat-laden vapors residing in it. Using high temperatures, the air conditioner compressor does what the name suggests it does – it compresses. More specifically, it compresses the vapor.

The Air Conditioner Compressor Cycle

Air Conditioner Compressor


The compressor is the core of the cooling system of an air conditioner. Although the process itself is rich in details and technical information, we can narrow down its purpose to several main functions which constitute the working cycle of the compressor.

A Compressor Compresses

As we previously mentioned, the main function of this part is to pull in from the indoors cool refrigerant gas. Once it goes through the component, it’s heated curtsy of high temperatures and high-pressure processes and then exits at high velocities as a hot gas.

Transfer of Heat

The air conditioner compressor expels hot gas toward the finned condenser coil found in the side of the air conditioner that meets with the outdoors. There, the fans blow the outdoor air through the fins and across the coil. The heat is extracted from the refrigerant and then transferred outdoors.

Liquid Turning

Once the air conditioner compressor extracts enough heat from the refrigerant, the latter turns into a warm liquid. The liquid gets filtered through high pressure until it reaches the expansion valve. There the refrigerant is cooled down and makes the transition from high to low pressure.

Heat Absorption

The journey of the refrigerant finally gets it to the evaporator. Because of the considerably lower pressure found in the evaporator coil, the chemical construction of the refrigerant forces it to revert to a gas state. In order for this process to be completed, it requires the intervention of heat, which is granted by the evaporator coil’s fans blowing over the warm indoor air.

This is the point when you begin to notice a change in your room’s temperature. The room heat continues to get moved to the evaporator and, as a result, the indoor air gets cooler. At this point, the refrigerant is back to what it was in the beginning: a low-pressure, cool air. Once released, it gets pulled back into the air conditioner compressor to start the cycle all over again.

Fixing a Faulty Air Conditioner Compressor

Air Conditioner Compressor


An air conditioner compressor isn’t necessarily something that can be easily swapped or repaired at the snap of your fingers. This is mostly due to the fact that it’s strongly interconnected with the other mechanical parts of your air conditioning system. As such, it’s recommended to appeal to a professional if you wish to do any work on it.

But if you do have some basic technical knowledge, then you can afford to save the expenses of ringing an expert and doing the job yourself. Here’s how.

STEP #1: Make Sure the Compressor is the Problem

Stick out your hand in front of the air conditioning system. If no air is coming out or if the air is warm instead of cool, then you definitely have a problem on your hands. However, you need to make sure that the compressor really is the problem here. A faulty air conditioner compressor is actually one of the worst case scenarios, meaning that there are many other possible explanations that can come before it.

Perform some basic check-ups on your cooling system. As you continue to cross possible explanations off your list, you will gradually be left with only the compressor as the possible culprit. Some things that you need to check include:

  • Check that your unit is plugged in or that the socket has electricity running through it;
  • Make sure that the control settings on the remote aren’t messed up;
  • Investigate some other components that could have led to this issue, such as blower fans, duct work, and air filter. If something unruly catches your eye, it’s better to gear your efforts in that direction instead.

Some of the steps mentioned above do sound a little bit basic, but things like these can happen to the best of us. It’s better to scratch off the possibility of a small slip-of-the-mind rather than invest time, effort, and even money in something that wasn’t even the problem.

STEP #1.B: Common Compressor Problems

You can go about it one of two days: problem arises, scratch off everything until you’re only left with the compressor OR problem arises, start with the compressor.

There is a set of particular issues that are nine-out-of-ten situations connected to the air conditioner compressor. If this problem arises, your best bets are checking the compressor first and going from there is something is wrong.

Improper Cooling

The immediate effect of a faulty air conditioner compressor is the unit not being able to expel air as cool as you’d like it to be. In most of the cases, the one responsible for this is the pressure control of the compressor. Any variations above or beyond the ideal pressure level can cause malfunctions, including unusually high or low pressure discharges.

If you want to, you can check where the problem lies manually, by taking a look at the pressure gauges. Grab your unit manual and look up the pressure gauge section, which should, among other things, tell you what it should read when functioning under normal circumstances.

If your actual readings don’t fit with what the manual is telling you, then this means that there might be a problem. In this situation, it’s best that you get a specialized technician on the job, as clumsy alterations to the pressure gauges can cause more harm than good.

Burning Out

When the air conditioner doesn’t even start up, the cause of this problem can be of many different types. It can also be because of a burned out compressor. If the motor wiring gets exposed to negative conditions or damaged, it can affect the electrical system in the unit and, therefore, the compressor. The result can be either a burned compressor or a short between it and the motor’s steel parts.

Rather than tending to this problem, it’s much easier to avoid it. You can prevent these kinds of damages by performing regular inspections to the unit’s electric system.

Hard Starting

The issue defined as “hard starting” is a pretty common one. It usually involves the unit having difficulties starting up or “stuttering,” more often than not being the result of the compressor struggling to properly respond to the “on” command.

It might be a one-time problem or it might persist. If it’s the case of the latter, you can attempt to fix it yourself by replacing the fuse or by making some repairs at the level of the wiring.

STEP #2: Check the Type

If you can identify with either of the problems listed below, then you can pretty much green-light the replacement of the air conditioner compressor. Naturally, you need to make sure that you’re going to purchase the correct kind of replacement. You can do this by checking in with your unit’s manual, which typically mentions the type of your compressor.

You can have one of the five main (unaltered and not customized) types of compressors:

  • Reciprocating;
  • Scroll;
  • Screw;
  • Rotary;

For further visual validation, you can check out a guide that can help you identify the look and the technical composition of each of these compressor types.

STEP #3: Take out the Refrigerant

IMPORTANT! Before you attempt any operations on your unit, it’s crucial that you disconnect it from the electric supply. Not cutting off the power beforehand can result in serious injury.

Now that you’ve taken all preventive safety measures, crack the cooling system and remove all traces of refrigerant. Before proceeding with anything else, cut off all the refrigerant lines.

STEP #4 Take out the Compressor

After you’ve taken care of the aforementioned steps, it’s time to take out the compressor. As a general direction, an air conditioner compressor is usually found outside. If you have trouble locating it, consult your manual.

STEP #5: Unbolt the Compressor

Unbolt your compressor before proceeding while also making sure that you remove the hosing.

STEP #6: Swap Compressors

Using the mounting bolts, install the replacement compressor within the condenser unit. Reconnect all of the refrigerant lines. And speaking of the refrigerant, might as well replace the coils while you’re at it too.

STEP #7: Finalize

Assemble your unit once again, reconnect it to the power source, and check if your problem is fixed. If any further malfunctions appear of it no results show, it’s time to call an expert and avoid accidentally having it develop into a more pressing issue.

Bottom Line

With this short guide, we hope that you’ve got the general gist of what an air conditioner compressor can do, what problems can arise from its malfunction, and how you can fix these issues. We mention that if you’ve never had any previous technical experience, it’s best to do everything under the supervision of a technician.

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