Testing if an HVACR Compressor is Shorted to Ground, Open, or Overload Tripped!

In this HVAC Training Video, I show How to Troubleshoot if an HVAC/R Compressor is Bad. I show if the Windings are Shorted to Ground, Open, the Internal Thermal Overload Protector is Tripped, or if there is a Bad Electrical Connection. I Measure the Electrical Resistance across the Terminals of a 1 Phase and 3 Phase Compressor and I show the inside of a Burned out Compressor. A Compressor Burnout leaves acidic residue throughout the inside of the system. Supervision is needed by a licensed HVACR Tech while performing tasks as Experience and Apprenticeship garners Wisdom and Safety.
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[@acservicetechchannel]

-Join our updates list for an email strictly from us for new videos, articles, products and website features! www.acservicetech.com Mini Split Book on Our Website- www.acservicetech.com/mini-split-book Mini Split Book on Amazon- amzn.to/3ytHJSs Mini Split Book on TruTech Tools- www.trutechtools.com/BooksGuides Mini Split E-Book on Google- play.google.com/store/books/details?id=HN-iEAAAQBAJ Mini Split E-Book on Apple- books.apple.com/us/book/id6445178399

[@paulpeter2869]

Hi Craig! Love your videos! AMANA furnace with a B1 code (module not communicating with blower motor) emerson aa25650l variable speed. Meter reading from R-W is 0.04V at the control board and the rest of Tstat wires are 27V. Do you know what could be the problem? Thanks very much!

[@paulpeter2869]

The motor is working fine as per ohms test at the 3 pin connector

[@dayjavu2586]

Do you have a video on low, medium and high temp compressor difference?

[@pehvac9198]

Thanks for all the amazing knowledge boss

[@abelmouzount8817]

Hi I just had A unit where we put all new wiring box / outlet then change the capacitor but end up with no running fan after ordering a motor fan condencer got it changed the fan started working but the house isn't sending a cool air in the house ?? So I'm afraid there's a problem with a bad compressor or just cuz of the hot weather that I need to hose it down with water then cool it off then try it works? I wish I could get some guidance from anyone here that faces similar problems? Thank you

[@newstart49]

Great video!! Suggestions and beyond ; 1. If the IOL is stuck open and it shouldn't be (Cold compressor etc), try hitting it with a 2x4 to unstick it temporarily until the repair/replacement can me made. Sometimes a sudden shock will get it to close. Sounds unprofessional, but if you get it going for the weekend, you're a hero! 2. After turning off the power to the outdoor unit, push the contactor fully in- to make sure the power is off and to bleed the capacitors at the same time so you don't get bit. Check as well with the meter to make sure power is off. 3. If nothing is running outside and it should be, don't be fooled. A bad duel capacitor can cause the compressor and the motor both to overheat and shut down. 4. Plastic forceps come in handy for quick connecting a temp wire or meter to another wire or capacitor for testing. 5. Always test a grounded compressor at the compressor itself, the wiring to the compressor may be shorted to ground (Made that mistake one cold day covered in snow- but only once) lol 6. A float drain switch in the main drain can flicker the low voltage on and off quickly causing chatter at the outdoor contactor and also cause the scroll compressor to run backwards resulting in a no cooling situation and a noisy compressor complaint. Install a time delay relay in the circuit and set it for one minute minimum. 7. Always verify your meter is working by testing it on live voltage first! Assuming the power is off because you don't read voltage just might mean your meter just quit working. I've enjoyed HVAC work for over 48 years and I still love it!

[@muneycorn6310]

Love your videos Mr Craig ...You and Mr Brian (kalos) are great teachers.Invaluable to those of us learning online.

[@j.bennett2485]

Hands down the best teacher and KZbin channel on here. For someone who likes troubleshooting and fixing their own equipment these videos are incredible.

[@CappyCraigZ]

If you get OL between any terminals, common to run, run to start, start to common, you’ll get OL on your meter. That’s means the winding is open. It’s possible to just have one of the 3 open, 2 of 3 open or all 3 open. If the compressor is severely overheated the windings will be open until the internal overload resets. You can cool the compressor off with cold water or ice. A lot of times you’ll hear the internal overload reset, it’s a mechanical “click” noise. If you check any terminal to ground (any terminal to copper ref line works best) you’ll get continuity or a “beep.” If you get a beep on any that compressor is dead. On a 3 phase compressor all resistance (ohms) from terminal to terminal are EQUAL. On a single phase compressor common to run and common to start=start to run….run to start is the LARGEST RESISTANCE VALUE, common to run is the LOWEST RESISTANCE VALUE.

[@huskyng6981]

Hi Craig my situation is same like you mentioned Compressor, , Start - to run 2.9k ohm, and common - to start =OL, and common - to run = OL OPEN, And I haven't turn on ac for days even crazy hot weather too, is there anyway I can fix it??? And I also check , common - to ground green =OL, Run - to ground 39k ohm + and meter ohm keep on increasing, and Start - to ground 39k ohm+ meter keep increasing???is there way to fix or I have to replace a 5 months brandnew compressor?? Thank you for your help and your time

[@EarthaNell]

The contact is pulled in, but the compressor nor fan start. Got readings for compressor wires and terminals, but one wire from condenser fan had no reading. Will dead fan motor prohibit compressor from starting? 1996 Goodman 3 phase condenser unit.

[@abnergarcia6252]

Great vídeo! I would love to see a video where you troubleshoot a compressor with bad or weak valves.

[@harpoon_bakery162]

Thanks for keeping parts that went bad. That helps tremendously to lock on a visual.

[@josepalacios627]

Im working on a unit rn with compressor windings that are good but it doesn't start. I tried that grounding test and that's what it was. Im so grateful you made this video lol

[@soheil7673]

This tutorial very useful. But that's part of compressor checking. That's electrical checking only. What if the compressor is seized. Or weak. One of the best solutions checking mechanical functionality would. Be pump down the unit to see if it pumps down correctly or not. On the other hand all inverter units have same winding resistance as the inverter controls the load of compressor by increasing and decreasing the Amp and volt rather than winding. Big like to all your efforts during last couple of years. Appreciable

[@joseorta9928]

Great explanation...Im a minisplit tech in Apodaca Mexico...in yr videos I learn alot...

[@rolandotillit2867]

When the shaft seal is puking out oil and refrigerant, the compressor sounds like a bunch of marbles when you try to run it, and there's metal paste in the discharge line, I assumed it meant the compressor was shot, good thing this video exists to make me reconsider.

[@resurgensix]

You helped me out diagnosing this today. Thanks!

[@JuanGarcia-qu8ms]

Thank you for your help, I have learned a lot with your videos, I have already started my own business, I really appreciate you help. Thank you.

[@emmaa427]

Thx for sharing your knowledge!

[@2169scs]

Very good education on AC compressors , thanks

[@scetchport]

Easy to follow info. Thanks. In process of testing those in dometic harrier inverter rv airconditioner.

[@jimbola77]

awesome! Craig thank you for sharing! all your videos are so well explained! have a nice and safe weekend.

[@acservicetechchannel]

Thank you for watching!!

[@tutata7228]

Excellent video, I'm not working on ac at the moment, but I still want to keep learning more and refreshing my memory 😊👍🏼

[@acservicetechchannel]

You can do it!

[@tutata7228]

Thanks! 😊

[@LloydAveryM]

This video was very thorough.

[@handyertanto76]

Thanks you sir, for delivering this information. It's usefull indeed and comprehensive. Greetings from Indonesia. 🙂👍

[@spartan5106]

Excellent video, thank you for sharing

[@Tito-hvac8]

Great video. Thanks💯

[@andyclark7927]

Well explained I would tell any tech to have a look, good job

[@apprenticephil649]

Love the video but perhaps showing how a compressor analyzer or start kit can help diagnose a bad compressor would be informative as well.

[@sewerat11]

What ohm setting do you recommend

[@ApartmentMaintenance]

Great video & explanation Craig 👍

[@acservicetechchannel]

Glad you enjoyed it

[@tshokaphiri8381]

Hi guys, im a service technician in Botswana and love the great work y'all are doing with the videos! Coincidentally i had a similar problem just the other day with a Maclaren 12000 btu packaged unit! The compressor was heating up and much like in the video the thermal overload kept it from starting! I did an ohm test, continuity test and ground test to the compressor and everything checked out! I also tested the capacitor and also did a visual test and still everything seemed legit! I then took the decision to remove the thermal overload to see whether the compressor would start (big mistake) long story short the compressor overheated and shutdown! Can you help on what could have been the problem and what could i have done different

[@AdamHuishStreaming]

helpful and great video. thank you so much

[@jaykesapalaran5434]

Wow thank you very much for sharing your knowledge ❤️🇬🇱

[@fernandocortes9420]

Hi I love your videos thanks for keeping us learning God bless you Sr 🙏🏼

[@acservicetechchannel]

Thanks for watching!

[@albertrubian2971]

@@acservicetechchannel Good day Sir First of all sorry to how can i speak English but i hope you understand... What are the possible problems to compress Air dryer with alarm overload and everytime i turn on the breaker it always tripping (3 phase)

[@guyinpajamapants6892]

Always check at the taps!!!

[@brianb5779]

Damn excellent video and information so thank you..

[@igorshapovalov8527]

Thank you, very helpful

[@nihalahmadpasha7607]

Good for every technician thanks

[@acservicetechchannel]

So nice of you

[@francisguchie1973]

So detailed - I like

[@phongpham1453]

thank for sharing your knowledge.

[@acservicetechchannel]

My pleasure!

[@bineshchauhan8713]

Wish you long live and better doing Happy teacher day 💐

[@Mudo94]

Thanks for your videos man!

[@acservicetechchannel]

Glad you like them!

[@tytig94]

I have that same meter! I love the dual temp probe feature, and LRA/inrush option. Also the min/max option is cool. Great video, thanks.

[@tytig94]

Also your vacuum videos really saves me a lot of time. I use your 3 core tool removal tool method with 2 hoses, I pull a vacuum in 5 minutes or less with valves open! My company wants me to train everyone on how to do it, I did give you credit. I wish more guys would spend time mastering their trade away from work.

[@noeeon9910]

You guys make me want to learn the trade!

[@Boojyman]

A good meter will tickle your peter

[@zekenzy6486]

Great Video. Have a nice weekend and Holiday. Thank you for sharing ^_^

[@acservicetechchannel]

Thank you for watching!

[@jcmendoza8285]

you guys are a great source of Knowledge Thank you!

[@acservicetechchannel]

Thanks for watching!

[@Gabriel-vz7ml]

Thank you!

[@simpliciocamirino2271]

thank you for that sharing

[@frankduarte7109]

Great video!

[@romarro4616]

Awesome tutorial

[@acservicetechchannel]

Thank you for watching!!

[@mrman5374]

This guy is simply THE BEST!

[@acservicetechchannel]

Thank you for your support!

[@mrman5374]

@@acservicetechchannel No really thank you for what you do! We live in a time where training is so poor, but you have helped me tremendously!

[@michealmanuel2143]

Very very good information sir Thank U very much 👍

[@acservicetechchannel]

Thank you for watching!!

[@rogerf3622]

Great informative video.

[@acservicetechchannel]

Glad you enjoyed it!

[@jesusadrianbarraza3061]

The best chanel for hvac hands down!!!

[@acservicetechchannel]

Thank you for your support!!!!

[@Gameboy_Steve]

Awesome thanks again

[@davidstofanak3222]

We just had our compressor fail after 2 years of service. Its a mr cool universal heat pump DIY install. We had an authorized MR Cool tech come out and diagnose it and covered its replacement but I'm worried maybe we wrong during the install. The Tech was super impressed with our work and said everything looks great but I'm worried. The compressor sits on ground level outside the house and the AHU is in the basement maybe 4-5' drop in grade. When we installed the line set we didn't install any oil return bends just kept it as straight as possible hanging them basement ceiling. Having a hard time researching oil return bends not a lot of quality information on it. I'm just worried if we replace the outside unit we would potentially be in the same spot in 2 years if we install it the same way. BTW your videos are awesome!!

[@clifordmichel8981]

Great video, Haiti represent

[@Reefertech]

So basically if the compressor is off on overload it would read OL between windings? And if it’s shorted to ground you would get continuity(tone) from the shorted winding to ground ?

[@specialK_hvac]

If you measure ohms between run and start but not common and run and common and start that's am internal overload that is opened

[@officerkrupke4966]

You would read continuity to ground on all windings since they are all connected

[@luiselizalde6757]

Excellent videos.

[@acservicetechchannel]

Thank you

[@hermesyanez1431]

very nice buddy how always!, i love it all your videos, i follew you from Honduras, regans master!

[@carolineandjaimegonzalez9839]

Smelling the refrigerant works too. Spraying just a little of bit of refrigerant in your hand and if its smell like burnout tells you that you have a burnout compressor as well. That's just another easy way to identify a burnout compressor.

[@acrservicesmathewr7565]

The oil will also be black. Or darkened. It does have a terrible smell when it burns out or I have seen a ton of foam which indicates liquid migrating to the compressor oil and sludging it

[@rodgraff1782]

Also the wonderful smell of phosgene gas.

[@romerogarcia960]

Great videos

[@hvacplayer3238]

Nice thx. How’re you liking that uei black multi meter?

[@joeyysossa4144]

Great video..

[@heatncool]

On thermal overload does it open 1 winding or 2? It opens winding between common and start? Or both between common and run?

[@ajenjohnson7413]

I do enjoy your videos, great job there, but I do I have a question. I have a heatpump ( portable ac) and it is kinda noicy and I did some research on that and I learnt about using something called ac compressor blanket which wraps the compressor completely to insolate the noise it produces, can I use that on my portable ac compressor? If yes can I make a homemade cushion ac blanket and use that instead? What is your advice, please let me know. Thanks👍

[@thanglian]

Thank millions bro

[@baz159]

Nice 👍 video, can you make videos on 3 phase compressor phase reversal rotation

[@goldhammer561]

Awesome video

[@acservicetechchannel]

Thanks for the visit

[@douglieberman6406]

That means we are looking a variations in current related to different resistance, or the resistance and current are inversely proportional. As the resistance goes down the current goes up !

[@omgsogood5524]

its also possible for the lower resistance leg to be your starter right? ie, you showed 1.7ohm as the start as its a higher resistance but on my sub zero, im seeing the LOWER resistance leg is indeed the start leg [ its the leg for the capacitor ] for BOTH compressors. funny thing is i've checked both compressors and resistance is good as well as no short to ground. but for some reason, the freezer side is just not getting cold. also checked the voltage going into the relay as well as the capacitor.. so kinda scratching my head

[@vsjapan]

Great video. What is it that is causing the ac breaker trip frequently? Checked all the electrical of the condenser unit and all seems to be good. The capacitor is new the fan motor has no issues the contactor looks good. Could it be the compressor causing it? If so how to diagnose and fix? Thanks.

[@thembones12]

Check the circuit breaker itself...Make sure that ac breaker it not warming up or hot when you start/running the compressor, check the temp of the circuit breaker-using HVAC infrared thermometer...Also, With your HVAC clamp on ammeter, check the Starting Load Current SLA and Running Load Current RLA...

[@vsjapan]

@@thembones12 Thanks for the reply. Just for your information, it was the compressor. It was overloaded with Freon. Overcharged with the Freon. Recovery of the freon did the trick. The breaker has not tripped since then. Thanks.

[@TheWpruden]

A megommeter should always be used to test integrity of winding insulation. Not a multimeter.

[@rodgraff1782]

Finally someone who knows how and when to use a megger. I have three AMEC megohmmeters, crank style. It is the proper tool for checking the condition of the insulation on the windings to ground. If a system has moisture or contaminants in the oil, it will fail a megger test.

[@user-el9kp7yk2o]

Very good

[@acservicetechchannel]

Thanks

[@armandogeronimo8141]

Good day sir amassing tectnic

[@ismailahmed8031]

good job

[@acservicetechchannel]

Thanks

[@monteglover4133]

Not all failures are burnouts. There are 3 types of Compressor failures opens, shorts and burn outs. A standard VOM may not find a high impedance short to ground a merger maybe required. I’m a HVAC&R service tech with 40+ years of experience.

[@monteglover4133]

Generally shorts to ground are not a burnouts or have significant amounts of acid in the system. A burnout will generate acid from insignificant to severe and often create sludge if any doubt use an acid test kit. At a minimum a high capacity liquid line dryer should be installed when changing a compressor and the refrigerant should always be changed.

[@eliogonzalez3038]

Thank you so much for your help 🙏 and it help me a lot God bless you

[@miguelurbina3004]

Yes definitely a megohmmeter is the right tool for this a vom is not capable of reading such values

[@TheWpruden]

Every hvac tech should have a megommeter to test for those high impedance shorts!!!

[@monteglover4133]

@@TheWpruden even the cheap ones, will work if it has a high voltage test mode

[@mikemorton6219]

If you get acid smell from refrigerant, it's a bad burnout. Put ammeter around all 3 compressor wires. If meter moves at startup, compressor is grounded.

[@shaneisaac1184]

Hello Craig, which of your books would be best to learn the fundamentals of hvac split and troubleshooting methods? Am trying to save costs by DIY as much as I possibly can. Thanks.

[@samersarah957]

Is that better prove or using merger? Thanks.

[@belkacemfekkane2199]

an alarm (compressor B fault) in a 30rqm / rqp 160-520 heat pump. Is the problem in the soft or the ccompressor?

[@mickeylojkar5769]

On a 3 phase compressor, 2 windings reads the same. One is higher than the other. Is that term called shunted winding?

[@steelod1528]

Hey craig could you do vids on light commercial equipment not too many vids on that

[@SpottedEagleOwls]

I have made a mistake by swapping the LIVE and NEUTRAL wires. Will this damage my compressor as my input and output pressures always stays the same ?

[@douglieberman6406]

I would like to try white neutral line to neutral bar in breaker box for common of compressor, as start to common L1 Run to common L2 And common a neutral line to breaker box neutral. 2 breaker switches for compressor, one for L1 and other for L2 . It just that neutral (white ) is common and also hook up the ground line! Same goes for the 240 volt e c m . ! Just like a 240 v a c light bulb with 2 switches and one neutral.

[@abmtz8537]

Is it normal for my ac compressor to be wet from the thicker copper line down? It’s also taking very long to cool down my house.

[@DaLeSy.]

What did you set your multimeter to when checking if it is shorted to ground?

[@MrRalph438]

Have your book and quick cards, Posters are also helpful. Recommend them to everyone in HVAC Trade.

[@acservicetechchannel]

Thanks a lot Ralph!

[@sonamtobgay1797]

Plz can u explain me why my cold store getting off time and again..I had change contactor also

[@RitinPali]

Daikin 1.5 ton inverter split ac. 5yrd old. R32 gas running pressure 150psi. Current 6.3amps Both indoor and outdoor coils have been cleaned. Service Technician says it's ok. But it's not cooling. Temp in the indoor blower showed 16'c or 60'My brand new split AC showed indoor temp at 6'c or 43'f Previously compressor would heat up and trip. So got the outdoor pcb repaired. Now it doesn't trip but keeps running. And does not cool the air. The discharge line had a bad pinch in it. It ran throughput last season. Am out of ideas any help greatly appreciated. TIA

[@Thomas-eh8lb]

Why cany you clean the coil if you can clean the lines? Thanks

[@TripCoolLang]

Hello I have a 35 years old GE fridge I get resistance from the compressor Common to Starting reading is 2kohms, Common to running 25ohms, and starting to running more or less 2k. Is the compressor ok? My fridge is running but normally it runs loud but now my compressor runs more silent and turn off after few seconds or minutes. I test also the 3 pins of the compressor to ground it has a resistance about 10kohms. So I need to replace compressor?

[@solomonkariuki4797]

Hi, so much working on ac in gulf. I have a question about central unit. Single room the thermostat is no switching on.

[@acservicetechchannel]

look up "acservicetech testing thermostat with multimeter" thanks!

[@techdan7098]

My technician came today and put the clamp on the black wire while the system was running. He said the compressor was bad based on that reading alone. What should be the voltage when connecting a compressor to the black common line while running? Can you really tell if a compressor is bad by just clamping the black wire?

[@mlwee6796]

You disconnected the wire from the compressor in the split unit. Is there any residual power or current in the compressor? Any precautions needed?

[@hypocrisyrulessociety]

gotta use caution with the capacitor !!! KZbin how to drain "entergy" from capacitor

[@toupsclassroomtoupsclassro9557]

question: ok, bad transformer in heat pump. However the wire on the com. is red, so I'm assuming I connect this one to the white wire on the univ. transformer. Is this correct? Also, the white wire is on the 240 of the old one so I would connect the white wire to the orange for 240 the sec'd wires don't matter in orientation. Is all of this correct? ty

[@mustangracer5124]

I have an issue of occasional short cycling in my roof a/c unit.. will work normal 4 or 5 times then short cycle.. sometimes it does it first run.. other times it will not do it at all.. is there something i can check or replace that is intermittent failing?

[@techfive7202]

I had a carrier 2 stage residential compressor that threw me off. All terminals with plug removed showed continuity to ground but the terminals ohm out at .6 .8. .2. Not exact numbers but close. Normally the ohms are higher plus I never seen them add up when it is grounded. The compressor had 2 plugs which I never seen before. The other plug had only 2 terminals that I did not test. It was 2 stage obvious. Would trip breaker as soon as the unit turned on. Unplugged compressor and the fan would run. Another odd thing is it would trip as soon as I put the disconnect in without the contactor engaged

[@hectormedina9009]

Continually blowing

[@jackmcdonald7391]

I read ohms to ground between a compressor winding and the copper line to it and when I plugged it in it ran just fine.It was a scroll compressor.Not sure how it was possible but I almost condemned it for no reason

[@marvinostman522]

I have had this scinerio a few times. Compressor blowing the breaker. Testing at the compressor two windings had continuity to the tubing but not the third. The two shorted show continuity to each other but not the third. I ordered out the new compressor and someone else goes back and later tells me there was nothing wrong with the compressor. The fan would test out fine. Can an open overload create a path to ground? I did have someone tell me not to use too high of a range on the meter because it can give a false reading. I have been using just the straight continuity setting with the tone.

[@chefeatsher]

An open overload would not cause a path to ground. It would just prevent from the control relay coil energizing.

[@delroymorrison7599]

If the COMPRESSOR show normal no reading is it good or further testing is needed

[@tonyp6088]

Is it possible for the compressor to test ok accross the terminals but when it's powered up goes to earth? I'm having that issue at the moment. I have OL from terminals on compressor to the housing. But when the compressor is running there is voltage in the housing causing it to trip the curcuit breaker.

[@turbolag98]

Is it a failed compressor if the compressor is pulling double LRA even after installing a hard start kit but the windings have continuity? Compressor isn’t tripping the circuit breaker either

[@specialK_hvac]

Yes that would be a failed compressor if it is mechanically locked up like that. Sometimes you can give it a bump and it will free up but that's a stop gap solution

[@donniesmith8779]

If a compressor is locked up, is it still in a bad spot and not good?

[@CHOPPA78]

Not on All compressors tho ,,if it sn inverter values would be the same on each approx 2 ohms could you confirm?