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

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

greetings

If you get completely on your meter from one of the terms on the compressor

Ours want to start up , but won’t you can hear it engage but , will not start up , is our condenser gone or is the capacitor

So when ohm is high=burnt winding? And if there's resistance from compressor to ground showing resistance =shorted to ground? Because that means is connected

So we had a power outage and then suddenly the ac breaker tripped. Now it trips the second the ac unit kicks in. It appears to be the compressor itself, however, it measures fine and does not appear to be shorted to ground and everything measures out normal. Could it still be a bad compressor or something else? I disconnected the compressor and just let the fan run and it stays on without tripping. Kind of irritated the a/c tech came and didn't even do any measuring and just immediately insisted the compressor is bad.

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?

This video was very thorough.

Megger..

Thank you!

How do you know when the compressor all 3 has to be the same value and when the 2 has to match the 3 value

C-S= 3
C-R= 3
S-R= 3

Thanks

AND

C-S= 3
C-R= 2
S-R= 5

Or as the resistance goes higher the the current goes lower !

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 !

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.

Dude is ripped…

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.

What if my start to run ohms don’t add up right. Like 30% off?

So detailed - I like

Waoh amazing video thank you

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

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

anyone trying to give me a half page summary of what this video is about so i dont have to watch it?

Excellent video, thank you for sharing

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

This isn’t a good test for a compressor down to earth. Please be aware.

You’re missing one of the possible diagnosis. It is called a turn to turn short . If the resistance readings don’t add up like in your example,something is wrong with the windings themselves. Insulation has broken down and the windings can be shorted to each other, or a individual winding can have a turn to. Turn short. Compressor windings should also be tested to ground with a megger, which is a high voltage insulation tester. It will find ground faults that your 9 volt ohmmeter can’t find.

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!!

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!

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👍

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

OL means "open loop", not "open limit or open line"

I'm very confused now, I thought the second one is the run.

What about high OHMS? Common to run 33 OHMS Common to start 1.2 Start to run 33

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

I called technician over my fan not starting after a power outage on the community. After he came and inspected I noticed that the circuit breaker was not fully engaged and after fully place that in the right place. He can started unit and the fan start spinning. He proceed to take out the fan and got into the unit and mess with the therminal plug it slightly out and then place the fan back and started again and told me that I have to replace the whole compressor because now I have a freon leak. How can an electrical issue not causing the dan to spin, will make the the final to blow when all the pins are present and the AC Wwas not on for longer than a minute and no creo was added??

Very good education on AC compressors , thanks

Good day sir amassing tectnic

Great video, Haiti represent

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.

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

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

Does anyone know why I am reading 0.6 ohms between run and common but then OL between start and common and also OL between run and start?

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.

I had a 1 year old units blow a terminal on the compressor while I was testing it. Cause a premature bowel movement. Sorry ozone

In the description for the video they forgot to mention a short Turn to Turn. Learn to ask can she run. C+S=R

oil/&

Continually blowing

Multi- meter

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.