Replace HVAC Compressor for Air Conditioner Repair - Question - Richard - I am an HVAC technician and have read all of your articles on refrigeration and compressors. Great information and it has helped to hone my skills and offer better service for my customers. Thanks!

I was wondering what your experience is with replacing compressors. How do you decide to replace a compressor technically speaking, of course? Do you recommend repairing the air conditioner by replacing the compressor or replacing the central air conditioner?

I look forward to reading your answer. Brett Des Moines, WA

A condenser which houses the compressor in most HVAC systems

Replace HVAC Compressor | Air Conditioner Repair Answer

Replace Air Conditioner Compressor | HVAC Refrigeration - Answer - Brett - Thanks for the great comment, and hopefully, I can help you. Of course, with many of the questions I get, I have to assume a few things.

Things such as residential or commercial. While most of it is the same, there are some minor nuances that you need to understand or know when making the distinction between residential and commercial HVAC refrigeration.

I will assume you are talking of residential air conditioners or heat pumps and making the decision as an HVAC technician to replace the compressor when a failure occurs. Of course, your compressor troubleshooting skills are definitely important when you come to the conclusion that the compressor is bad.

I have been behind unscrupulous or ignorant technicians who told the customer the compressor was bad only to find something else very simple that fixed the problem. It was an easy process to get the compressor up and running again. You do not want to make that mistake because almost every customer will call for a second opinion especially when you tell them the cost of replacing their compressor in their air conditioner or heat pump.

So make sure you are 100% certain in your compressor knowledge and troubleshooting skills before you condemn an HVAC compressor in an air conditioner or heat pump. Your customer will appreciate your expert skills also. It’s simple, make sure you check all the basics.

Replace HVAC Compressor | Air Conditioner Repair - Breaking it Down

Residential compressors in air conditioners and heat pumps are hermetically sealed and it is impossible to take them apart and check for a bad piston or bearing or check the oil level.  With any compressor failure, you can have either a mechanical failure or an electrical failure. Since the compressor has an electric motor inside of it and because it has mechanical components inside of it an understanding of how each type of compressor works will help you understand the compressor and different things that can go wrong with the compressor.

Replace HVAC Compressor | Air Conditioner Repair - Due Diligence Troubleshooting

Another thing to understand is why the problem with the compressor happened in the first place. If the compressor locked up then you need to find out why it locked up? If the windings are burned up then you need to find out why the windings are burned up. Some of the answers to those questions are easy with some of the answers are not so easy. One time I spent hours trying to find out why a compressor failed and finally I found the problem. It was a problem that resulted from the poor installation skills of the installing contractor.

A small bead of solder had found its way into the piston metering device. The bead of solder would plug the metering device and cause the head pressure to go very high. The bypass valve in the compressor opened but it happened often enough that eventually the reed valves inside the compressor either busted or bent way out of shape. Anyhow, the customer appreciated my diligence even though their patience wore thin with my relentless troubleshooting to find the root cause of the problem. I didn’t want to simply replace the compressor only to have it fail again.

The bead of solder would plug the metering device and cause the head pressure to go very high. The bypass valve in the compressor opened but it happened often enough that eventually the reed valves inside the compressor either busted or bent way out of shape. Anyhow, the customer appreciated my diligence even though their patience wore thin with my relentless troubleshooting to find the root cause of the problem. I didn’t want to simply replace the compressor only to have it fail again.

Electrical – Replace HVAC Compressor

The same can be said about burnout. Burnout is likely the result of poor installation practices by the installing contractor and boils down to a lack of proper refrigeration training and poor education of the installing HVAC technician. When a compressor burns out and you find the electrical part of the compressor has a problem from your troubleshooting skills (such as Ohming the Windings) then you need to test the oil for acid.

It is not always the case but sometimes when you have an electrical problem it is from poor installations the installer did not properly evacuate the refrigeration system and get all the moisture out of the system. This created a problem with sludge and producing acid when the moisture mixed with the oil. Eventually, the acid eats away at the windings and you end up with shorted windings.

Compressor Repair or Replace?

It happens and no matter how many times I tell homeowners that the lowest bidder is not always the best many times they go for the lowest bidder and end up paying way more in the long run than if they would have chosen the contractor that may charge a little more but the job is done right especially with the new installation. On the other hand, I have run into some true knuckleheads who say they know what they are doing but really do not because they never learned how to do it right in the first place.

I’m talking about installing a new air conditioner or heat pump and getting it right the first time with the refrigeration system. Always use nitrogen and a micron gauge for deep vacuums. Do the triple evacuation. In all the years I have been doing this I have never had any one of my customers call me back because of a burned-out compressor because of poor installation skills.  I have had problems with defective compressors or a condenser that got struck by lightning but never had the oil come back positive for acid after one of my installations.

Mechanical – Replace HVAC Compressor

Mechanical lock-ups are becoming less and less frequent because more people have delay timers in their newer thermostats or the equipment has a delay timer in the system somewhere. And I have some stories to tell about delay timers but for brevity’s sake will refrain from telling them. With the old mechanical thermostats, with a heat pump or air conditioner system that does not have a delay timer installed in it, a customer can innocently kill their compressor. How? By short cycling, the on and off switch too fast.

They go turn it to cooling mode and then change their mind and turn it off and then turn it back to cooling when it was already running and the compressor cuts off and then back on again in fast succession and you have caused a compressor to be mechanically locked up.  Since the compressor is hermetically sealed it is impossible to tear it apart and unlock it. Sometimes it can be forced to restart and sometimes it cannot. It is still a problem and needs to be addressed.

A good technician is always looking out for the customer and will recommend a fix for this whether it is changing out the thermostat or adding a delay on break relay in the system at the “Y” contacts.

Replace HVAC Compressor | HVAC Repairs - Conclusion

Finally, a good HVAC technician will always strive to learn new things and give the customer the best service possible using that knowledge. When you make the recommendation to the customer to replace the compressor make sure you tell them that you know why the compressor failed and that you will correct the problem with the compressor so it does not happen again.  Make the repair and you will have a happy customer that is confident in your skills and this customer will tell others about your service and you will stay busy.

Replace HVAC Compressor for Air Conditioner Repair

Technical Resource: Refrigeration and Air Conditioning Technology