How to check the windings of a refrigeration compressor

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
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.

[andrewmack]

Well done you would be amazed how many engineers do not know this and how to check a compressor

[doncocorote]

I have learned more with your videos than school. Thanks 🙏🏼

[MrBlaklip]

I really appreciate your simplicity along with a visual of your meter readings

[yongminhuh]

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!

[grayfurnaceman]

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

[grayfurnaceman]

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]

I'll try to keep them coming.
GFM

[grayfurnaceman]

It is single phase. If it was 3 phase, it would be the same resistance on all 3 legs.
GFM

[ChrisV-]

Good video, just starting to get into hvac myself.

[mpugliano]

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!

[arnelespena]

Thanks for the upload of this video. I learned a lot!

[SamsFootballFreestyle]

nice video man good tutorial even ppl who dont understand can understand this video

[PigSpinnin]

test worked perfect. Helped me narrow the prob to a bad cap. Thanks for posting this!!!!

[goonzsquad]

So Gary your not actually putting your leads inside the terminal, just clipping to that metal part ?

[mtbbiker]

I can't access the compressor plug directly (5 ton Trane unit), but I checked it at the wires after disconnecting from the contactor and capacitor. My numbers are 1.0, 1.4, 2.0 so my total is off by -0.4. Does this mean the compressor is going bad? No grounding issues. It's currently pulling 21.5A (105 degrees ambient temp) on the common wire (followed your other video). RLA is 26A. It's a 14 year old 5 ton Trane R410 heat pump. The compressor is noisy at start/stop but otherwise seems to run okay.

[grayfurnaceman]

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

[jgvaz]

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

[jonerasmus]

Make a vid of testing a single phase motor without marked leads plz .

[grayfurnaceman]

Ok. I misunderstood your comment. Are you using a digital ohmmeter? Set at the X1 setting? Is it a very small compressor?
GFM

[SamsFootballFreestyle]

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