How I Troubleshoot an Air Conditioner Compressor

If you are researching how to troubleshoot an air conditioner compressor, you've come to the right spot. In this video I will describe step by step how I troubleshoot a compressor.

As someone who has been in the HVAC field since 2010, I can show you How I troubleshoot an air conditioner compressor. It's a step by step process that tales patience, but also takes a good bit of knowledge.

First troubleshoot for a short to ground. Before going anywhere, check at the contactor to see if anything is shorted to ground. Put your meter setting on "continuity" check. Put one meter lead on the left terminal on the load side of the contactor and one to ground. Do you have continuity there? Try the other load terminal to ground. Do you have continuity there?
If you have continuity at either of these terminals to ground, then something downstream is shorted to ground. Now you just have to troubleshoot it. It could be:
1. Any of the high voltage wiring.
2. The contactor
3. The capacitor or start capacitor
4. The condenser fan motor
5. The crankcase heater
Measure the line voltage coming from the house
Ohm out the compressor at the air conditioner.
I usually just do this with the wires at the service panel still connected to the compressor. If I see something screwy, I'll make an effort to check at the terminals themselves.
Internal Overload on the compressor can happen when it is running so hard the compressor heats up and shuts down to protect itself.
Ohm out the windings of the compressor. Check your ohm's with your multimeter reading between Common and Start, Common and Run, and Start to Run. Without going crazy in-depth on it in this video, generally, you'll notice the resistance between Common and Start will be a little higher than Common and Run. The total of those two numbers is what you'll read between Start and Run. So, if you had 2.3 ohms between Common and Start and 1.7 between Common and Run, you should have about 4 ohms between Start and Run.
Does it have a locked rotor or a stuck rotor? A stuck compressor can be fixed with a hard start kit. It can give it a boost that is needed to get the compressor moving again.
So many things can happen to a compressor to cause it to fail. Not only do you have to diagnose the bad compressor, but you also have to find out why it's not working.

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0:00 Intro
0:45 Check for a short to ground
1:23 Ohm out the compressor
3:23 If the windings are good, check the breaker
5:04 Locked rotor / Hard start kit
5:43 Measure the line voltage to see if it dips
6:08 Bypassing the compressor to see if the fan is good
6:44 Internal overload on the compressor
8:19 Bad valves? Are you sure?
9:17 Some other things to check

[abdelouahhabmellouk]

It is really a great help for new hvac technician. Excellent job !

[victorebolum]

I think the instructor rightfully assumed that any technician would cut power off the unit first.
This was a thorough instruction on the nuances of trouble shooting and understanding how units work.
Excellent presentation.

[robertjakk]

Good class, for a beginner like myself as a Rental Company.

It’s expensive to call a technical every time something go wrong.

Again thank you for beginning.

[Alienspecies]

I’m a service technician by trade and I still watch these videos after a long days work. Pick up my kid from daycare and hang out with her while watching videos and feeding her or bathing her whatever the case may be there’s an hvac video playing in the background

Great video, very informative

[rafaelretiz]

I’m so impressed with so much crucial information for those just started or even Senior techs.
Love this video, you nailed it.
Very clear, easy to understand video.
Kudos and keep those videos coming.

[christiandesantos]

Wow I just became HVAC certified from Delta college Stockton can and though I learned it all regarding this topic. I feel even more confident than ever now after see ur video. Ty so much

[bryanbennecke]

Most comprehensive, easily and briefly explained for a technician or DIYer. Your channel has saved me $100s and $1000s from your experiences and knowledge.

[zachsstrat]

Great video...I've been in the trade for years, almost all new construction, rarely troubleshooting. The information you're going over is clear and easy to understand. So awesome.

[eduardomeza]

This is impressive and hell of a way to save time and be professional on another level

[omarr.r]

Just started doing service calls after doing only installs for 2 videos help a lot

[metalliequus]

When you’re looking for the best explanation but then someone does give you the best explanation with VARIOUS possibilities and you just like alright take it easy haah ! Excellent video ! Time to get to work !

[mallkomoha]

This is absolutely fantastic the most convincing explanation in troubleshooting, this gentleman showed the international from where to tackle the problem .yes the contractor is the epicentre then you start eliminating. Excellent hint Well done sir!!!

[partshnc]

Noticed lately ! but ok....Greg Fox you have done a great job! By sharing this its incredibly helpful guide on troubleshooting an air conditioner compressor.

[hajjajchami]

Why some people did dislike that's ridiculous a lot of respect for this man

[leason]

That was one of the best videos I've ever seen. I'm not an HVAC tech, but I feel confident how to t-shoot mine now to save an expensive trip for something preventable. Keep up the great videos!

[ryantidwell]

Best compressor diagnostic video i’ve seen on Youtube! Great job explaining all the possible scenarios!!

[Barryd]

Excellent video. Learned a lot. Especially thankful for the tip on NOT removing the leads at the compressor because it may blow up in my face. I adorned a clear mask and removed them carefully. Sprayed some contact cleaner, attached, and it worked so I assume after 27 years of service the connections oxidized.

[murky]

I thought your lead in about being the best video sounded a bit arrogant, but having watched it, it is outstanding. Thank you for posting. I was a little surprised to see you explain going to a hard start kit before testing the run/start capacitor that is already there. Maybe that's just more efficient.

[HVACChillin]

Great video for all the DIY customers
Out there.

[sandrarichardson]

This is a pretty big learning curve for me....but you have a lot of meat in this video. I think after watching it many times, I will actually start catching on and be able to understand what you were saying...lol. Thanks for the help in advance. Jesus bless.