How to check the windings of a refrigeration compressor
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- čas přidán 26. 04. 2012
- Describes the use of an ohmmeter to check the windings of a single phase air conditioning compressor motor. Includes winding resistance and check for shorts to ground
This video is part of the heating and cooling series of training videos made to accompany my websites: www.graycoolingman.com and www.grayfurnaceman.com to pass on what I have learned in many years of service and repair. If you have suggestions or comments they are welcome.
If you are a homeowner looking to repair your own appliance, understand that the voltages can be lethal, the fuels are highly flammable and high pressures are used. Know your limits. - Jak na to + styl
Well done you would be amazed how many engineers do not know this and how to check a compressor
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I really appreciate your simplicity along with a visual of your meter readings
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I have learned more with your videos than school. Thanks 🙏🏼
Welcome
GFM
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You're so right! This ac hasn't been used for 20 years. I finally got it started it worked for 10 to 15 seconds, and then there were arching and fire burning of dead bugs, spider web and dried grass, etc.... I shut breaker off, and waited for 5 mins and then restarted it worked a several seconds there again arching and burnt rest of those stuffs. And then it finally died. I restarted again now just humming bird. I gave a closer look at contactor there are metal burnt color. I guess I have to replace contactor. Thanks!
Welcome
GFM
Nice explanation. Is your fluke multimeter suitable for windings insulation test to ground? Shouldnt it be a megohmeter with higher voltage to be sure theres no fault to ground?
Thank you
Thanks for the upload of this video. I learned a lot!
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wondering if theres any other important tests i should preform if i find a old or new compressor laying around to make sure its working properly etc
The meter is a Fluke 16, now replaced with the 116 and is a megohm meter. Also, some techs use an insulation tester to test the winding at a high voltage, which the windings are exposed to. For me the jury is still out on these meters, as they may diagnose a compressor as bad that may not actually fail for some time. Certainly, if the unit is high liability such as a blood cooler, I would use them.
GFM
I checked compressor its values are C to S :4.5ohms, C toR :1.55, and S to R : 6.5ohms when supply is given compressor gets over heat but Cooling wsa not coming give me suggestion to solve the problem.
Another great video!
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I have 2 at 17 and 1 at 34... which is the run and which is start?
So I know which is the common and that the two pins remaining are either run or start, but how do I tell which is which?
Well done great video ty very much!!!! I liked it so much i even watch the advertisement hope it puts a few cents in your pocket!
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So Gary your not actually putting your leads inside the terminal, just clipping to that metal part ?
Good video!
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nice video man good tutorial even ppl who dont understand can understand this video
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It is single phase. If it was 3 phase, it would be the same resistance on all 3 legs.
GFM
Like very use full
OL means there is no continuity. Windings should have continuity from one end to the other. Windings should not have continuity to the body of the compressor. Hope this helps.
GFM
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Thanks, Is that a ferret?
Thanks for the support.
GFM
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Good video, just starting to get into hvac myself.
Thanks alot
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test worked perfect. Helped me narrow the prob to a bad cap. Thanks for posting this!!!!
Welcome
GFM
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It's old . But old is good. Sometime you are getting ohm reading good but compressor lock out then you looking for the new compressor.
Thank you gray!!
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Thanks!!!
Thanks for responding to my questions! I think I figured it out where those wires are broken off - compressor relay. I wish if there's a way to send email.
You can send to Grayfurnaceman@gmail.com
GFM
I'll try to keep them coming.
GFM
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If I sent you a few pictures, can you tell me where did those wires came off? I believe those wires came off of relay but there are no visible sign( no screws joints, etc... May be grounded or chassis I don't know.
I can try. Send to Grayfurnaceman@gmail.com
GFM
Thanks alot.. Hope to see more good stuff like that.. :)
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Yes. When the 2 windings are read in series (R to S), they should read the total of R to C and S to C. Hope this helps.
GFM
grayfurnaceman What if you have 2.1 between common and run and 2.3 between common and start but only have 3.2 between start and run? Shouldn't I have 4.4 between start and run?
I have a trane dual unit heat pump the fan on top of the motor want shut off.but thermostat cuts fan off that blows through duct work into house.what is the reason fan outside want shut off?
Stanley Sanders I assume you mean the outdoor fan won't shut down. It could be the contactor in the outdoor unit is stuck on. If so, it needs to be replaced.
GFM
Hi, do you have a video on how to check on a 3 phase HVAC compressor windings? I recently have the compressor breaker tripping and I found out due to the compressor having no continuity on all phase ( L1-L2, L1-L3 & L1-L3 ). I also found the resistance to be very high.. around 300ohms between L1-L3 & L2-L3. Can i conclude that the compressor breaker trip due to the compressor bad/Open winding? I check the breaker & contactor, they are OK.I found so many videos here & i found yours to be the most helpful. Thanks in advance.
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Great vid. Thanks
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Make a vid of testing a single phase motor without marked leads plz .
The reason I asked is the numbers are too small. Most compressors will have single digit resistance in their windings.
GFM
Ok. I misunderstood your comment. Are you using a digital ohmmeter? Set at the X1 setting? Is it a very small compressor?
GFM
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Thanks for the video… hope your still active.
Still here.
GFM
@@grayfurnaceman man I’m in town take care of my mama & her unit was down & I wanted to ensure that I was troubleshooting the right way… thanks again brother & keep’em going.
Does the decrease in the resistance value between the common terminal and the start terminal imply that the compressor is malfunctioning?
Example, the resistance between the common & start is 1 while the resistance between the common & the run is 1.3 (resistance total between run & start is 2.3).
Noting that the compressor needs a start capacitor to make it running. Without that start capacitor, the compressor cannot work.
So, two questions are here:
1. Do these resistance values indicate an issue with the compressor?
2. Does this need of start capacitor to start the compressor indicate that there is an issue with the compressor?
Thanks
First, the resistance values should be compared to the factory specs. Generally, the resistance of the run to common will be the lowest.
If you are saying the compressor will not start without a start capacitor, and the start cap was not original equipment, either the compressor is on its last legs or the run capacitor has failed.
GFM
Hi. Thanks so much for your video here and BIG THANKS for explaining how to understand Ohm readings between C, R & S when l didn't know what they should be in the first place. I'm just using a basic cheap multimeter and assuming that '1' is equivalent to O.L. I hope I'm correct? As l cannot afford a high end Fluke such as the two you've mentioned (16 & 116), could you tell me what you think of the 101 model please? I'm new to electronics although I've been trying to understand how to accurately use a multimeter for years (and getting nowhere.. Lol).
Cheers.
1 is equivalent to OL. :)
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I don't understand OL meaning you have no resistance? meaning the windings are good?
open line or open load, how I heard it
I'm assuming you are using those new test leads that have zero resistance? Wouldn't you first short the leads together, find their approximate resistance, could be a few tenths of an ohm and subtract that value from your total resistance? To eliminate the error from the lead resistance, some people would use a four wire ohmmeter. Readingss of hundreds of ohms or more, who cares about a few tenths of an ohm, but when measuring resistances of about half an ohm, a few tenths of error can be quite significant, would you think?
Jim
As the potential resistance of the probes will be always the same, and the readings of compressor windings are comparative, I do not think it is necessary. And in fact, I have not seen the resistance of the leads be anything other than 0.
GFM
I will.
1:00 Are the two windings the highest resistance of the three combinations?
The highest reading it's the run and star ends
Loved Evercoat commerical
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yes sir
Hi there my compressor is not starting, I check the windings from common to start I have 2.6 and from start to run I have 2.7 and from common to run I have a 0 . what's wrong here?
If you are doing the measurements correctly, you have a shorted compressor. Check from a winding to the compressor body. You could be shorted to ground. In any case, the wires should be removed from the compressor before testing.
GFM
I got exactly what he got here. 3.0 / 2.5 / 0.5 but my compressor just shakes hums then clicks off. Tested the start run capacitor (only 5mo old) and MFD tested good on it. Contactor is sending 240V so I guess my compressor has a mechanical failure like a seized piston correct?
I would check amp draw. Should be locked rotor amps as shown on the compressor plate. Yes it is dead. The rotor is locked. Most common failure.
GFM
I've had several that the rotor was locked after sitting for a long time. On many of them, I've used a Rubber mallet and gave it a medium tap on the side a few times as I powered it up. This has unlocked the rotor but I would not count on it being a fix. It could buy you some time to repair or replace the compressor or unit.
thanks - Y T videos , for not to give up on my frig . watched it and decided to fix my Frigidaire if I could , even though I shorted cord (for millisecond) when I plugged it in during my attempted repair . little smoke , spark, burned off tiny bit of one prong was still nothing , since I quickly puled it out , compare to puzzle - why I had no more power in frig. I am not and never be a electrician , but I can do simple things . ( I left alig. clip on run tit of comp. touching other and grounded them all by axid. or beer ) did not even trip breaker , but lost power to ice box. period . after tracing all wires , connections , plugins , looking for fuse ?, I knew there is none , cussing , make beer run , I was about to give up . but I was goanna at last salvage bulbs and get rough with ice maker to fined out why sometime wasn't dumping cubes like 9 years ago . luckily box was still plugged in , while I for no reason wiggled temp. setting knob when and suddenly lights and blower come on . I was surprised and little pissed off , that I didn't think of check its relay as a first thing . instead of tracing those wires . anyhow , 9 year old side by side box was pretty much fixed by accident with new start relay , few hammer blows on comp. and some beer . so don't give up , cut corners if needed, keep trying and improving . thanks again for this video, it helped a lot , save some dinero $ and gave bid of a satisfaction . even with pukito buzz .
14 ohms doesn't seem that small to me, maybe the compressor is shorted somewhere. Thanks for your help though :)
Glad it helped.
GFM
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How do you know if the windings are going bad? Sorry if it’s a dumb question
If the resistance of each winding matches the manufacturer specs and there is no continuity to ground, the windings are ok. Not dumb.
GFM
thank you ,i found a good informatios here , i just want to ask you a question ,can we fix the windings of three-phase compressor?
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I couldn't understand clearly. Is that winding good or not. Usually when I checked motor or anything winding the good winding is denoted to three phases equal resistance of winding. That the winding is correct but here not like that
The winding is good. It is a single phase compressor.
GFM
good vid thanx!!!
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how about a 12v compressor, Im getting 4 all around
I don't know what design of compressor you have. If it is 3 phase DC, it would be the same on all windings.
GFM
I have another problem my compressor do not start - grounding test ok, ohm test between pins ok I did also another test I mean continuity between windings. . I was checking is there is continuity with meter probes and beep signal from meter. There is a beep only between upper and one lower pin, upper and second lower pin no beep - that means that compressor is broken electrically ?. To be more precise in tree possible combination of touching pins with meter probes there is only one beep + my connector was different from yours 1 pin in upper position + 2 pins in lower position. Please give your explanation,
Ignore the beep. It is only there to tell you if there is a very low resistance. Measure each resistance and record using a drawing. One should be lowest (1 to 3 ohms). The second higher added to the first should equal the 3d reading. If they read normal, the capacitor is good, the compressor is probably locked up (read dead). Hope this helps.
GFM
grayfurnaceman I checked that once again and it was ok electrically and did not mind about continuity test. So I looked deeper and started it finally (by wire) omitting all electronic boards in my device and it worked - so the reason was not broken compressor but poor electronic - now it works fine without it - for my application it is enough. Thanks for you help, and youtube clip that make me think
OL = Open Line
I am indeed, It's not too small no. I'll figure it out.
Why take the wires off? If compressor is still in unit it seems difficult to check this. Can you just discount the wires from contactor and capacitor and use the wires?
+Tommy Jarrett So, how would you feel if there was a short or open in one of the wires, perhaps at the connection to the compressor terminals and you diagnose a shorted or failed compressor. Oops!
GFM
grayfurnaceman excellent point exactly what happened to me the spade connector at the compressor was toast. Had to replace wire and coonector
If you know common, then hold probe on common. Touch other probe to a terminal and record. Then touch probe to remaining terminal and record. The higher number is start and the lower number is run. If you still are having trouble I can send you a diagram.
GFM
Hello sir will u give the diagram
Student from India
I changed the compressor today ...but I checked the wiring according to the diagram but it was keep tripping the breaker
Jawad Ibrahim Does it trip the breaker immediately or does it run for a while before it kicks off?
GFM
It was tripping immediately ...but I checked the compressor tag was in the comp was three phase but actually it was one phase compressor ...
it can be wrong wirring
It was one phase compressor instead of three that's why
1)I recently checked one single phase compressor, the connectivity is good (beep sound there), no ground value comes, comp is not grounded, but the resistance between the terminals is displayed as zero and the value is fluctuating in other terminals.compressor taking high amps 14.7amps recommended is 1.2 amps and gets tripped in olp. can you provide any solution for this issue,it is clear that the compressor gets jammed internally but i want to understand y the resistance value fluctuates, whether the problem is with the multimeter.
2) would you share what are all the abnormalities we can measure in a grounded compressor, will the compressor works by drawing high amps or it will not start itself.
its hi amphre. need to replace compressor
Are you using amps?
No. This test is the last test you do to make sure the compressor is the problem. This one will tell you if the windings are shorted or open to each other or if they are open or shorted to ground. Hope this helps.
GFM
So what are you using oms? What do you set your multimeter to?
Johnny onthespot Yes, ohms. When checking continuity of the windings, it should be set at 1X. When checking resistance to the body of the compressor, you should a megohm meter. Many of the newer digital meters are auto ranging like the one in the video, so you do not have to set it.
GFM
grayfurnaceman
That's the thing, they're both the same.
C S R,,,????
a compressor can fail electrically and mechanically.
It can. This one is just about electrical failures.
GFM