How To Check Compressor Windings With Multimeter

In this post, you will learn about checking compressor windings or testing compressor windings. As you that in the refrigerator or fridge compressor we have an electric induction motor that rotates the pump. In fridge compressor mostly in rated in single phase which has 3 terminals. I already publish a post about the start, run, and common identification guide on this blog.
Sometimes when our refrigerator compressor stop working or not running a problem then we must call a professional to test the compressor or refrigerator. But if you want to check your compressor himself then this post is for you.



In this post, I am telling you about some main and common reasons for compressor not working and about testing compressor methods. There are many problems which we face in the electrical refrigeration system and due to which or refrigerator or Air conditioner stop working. But this post especially about the check compressor motor winding.

checking compressor windings



Checking Compressor Windings Using Multi Meter

As you know that in single-phase fridge or air conditioner compressor we have internally instilled a single phase motor that consists of two types of winding which we called main winding (ruining winding) and Auxiliary winding (starting winding). But if the compressor has receiving the power supply and still not working or running then maybe its starting capacitor or relay is not working. But if you want to test compressor winding then follow the below steps.
First of all, I want to give an example of a fridge compressor

If you want to check your fridge compressor then flow the below steps.


  • First of all plug out the fridge main electric plug. or switch of the supply which is connected to the fridge. 
  • Then see the relay and find out which one terminal is common, start and run. The common terminal will be connected to the overload protector or connect directly to the electric supply wire. (note that direct wire was connected in those single phase compressor, in which the overload protector is instilled internally).

  • After that find out the run terminal, in PTC relay the 2nd supply wire will connect directly to the run terminals of the compressor, which means that the 2nd wire connects to the relay point and that point supply goes to direct a terminal of the compressor will be your run terminal.

  • Now you find out the common and run terminal of the fridge compressor. So the other wire will be the start terminal, otherwise, 2nd supply wire will be connected to the start terminal through a capacitor or heating resistor. (note that heating resistor is instilled internally in PTC relay).

  • Now you find and mark your compressor terminal. Now set your multimeter knob on connectivity text or Ohm. Now connect one lead of the meter to compressor common and other connect compressor uninsulated body place. Continue this process with the start and run terminal.

  • Now if you find our connectivity of winding and body then it means that your compressor winding is short with compressor body or winding is uninsulated with iron core. And if have not connectivity between terminals and body. Then flow the next step.


  • The next step to test its resistance between one another. Test the compressor by unsung the below method. So first read the below post, and flow the method to test the compressor.

How to identify compressor terminals?


  • Now if your compressor terminals reading shown the same as in the above post then your compressor winding is not burned or if it's shown different reading between common, start and run then your compressor winding is burned.



  • Now if compressor winding resistance shown the same as I have shown in the identifying compressor example then change your PTC (positive temperature coefficient thermistor) relay and com.. overload protector or capacitor and if still not working then call a professional.



Mostly in some compressor in which the common terminal is on the upper side then the left side will be start and the right-hand side will run terminal, and Danfoss compressors in which the common terminal on the downside the right side will be start terminal and left side will be run as I have shown in the below diagram.

compressor terminals diagram



How To Test or Check Air Conditioner Compressor Motor Windings
  • Now if you want to check the Air conditioner compressor then it's also too simple, in the air conditioner compressor we have labels in which the R, S, and C written or parked.


However, if this rubber label is not available or removed then follow the below steps.


  • First of all, the terminal of the air conditioner compressor terminal is connect to an overload protector or direct to supply wire is your common terminal. Mostly we use white or black color for common. The other supply wire will be connected to a capacitor and to compressor terminal will be your run terminal, mostly in split unit AC the blue color wire is used for the run terminal. And the other wire will be your start terminal which will be connected to the capacitor. Mostly this red color wire used to start a terminal connection.



  • Now set the multimeter on ohm or resistance tasting or use an ohmmeter and check the compressor, follow the same method as we use for the fridge compressor terminal. However, let's see the example.



  • If your resistance between common and ruining is lower than resistance between common and starting then all is right and your compressor is winding is good condition and if that shows different results then compressor winding is burn or cross.


If it's shown good results then flow the steps.

  • Now test the compressor shortage between Compr.... terminals with compressor body like fridge compressor and if the meter showed no reading then compressor winding is no shortage with the body and if it's shown the reading then it means that compressor windings are shortage with compressor body.



  • Now if you check compressor motor windings and not find any problem and still compressor did not run then change the capacitor and if still compressor not working then check the overload protector.


As you know the overload protector is connected to the main terminal of the compressor in series and if the compressor overload protector stops working or internally open, the compressor also stops working. However, these are simple methods for checking compressor windings of single-phase and now if you have any questions then you can use the below comments section.

Sikandar Haidar

Electricalonline4u.com is a hub of electrical and electronics tutorials and easy diagrams.

10 Comments

  1. thank u somuch for the information i love your blog is educating,i love tobe receving mail on your update espercial on Ac/fridge, tank you ones again.

    ReplyDelete
  2. intelegent person
    Pls send me detail information about compressor dryer

    ReplyDelete
  3. Very usefull and good educational Post by you.

    ReplyDelete
  4. It’s an amazing blog your writing skills are very good. Also, within your appreciation, I just want to add that if you are also facing some problem with your refrigerator and want to repair it ASAP then contact Airwin Aircon & Fridge Services where you will get professionals for your Fridge Repair Singapore.

    ReplyDelete
  5. can you follow same steps above if you are testing a 2 or 3horsepower refrigerator compressor

    ReplyDelete
  6. Air sanders are forceful and effective. air compressor

    ReplyDelete
  7. Very technical focuses you revealed in this post. Yeah, compressor definitely an integral part of our refrigerator and if it gets into unknown trouble, we have to face a lot of trouble. However, I dug your content very thoroughly and amazed with the technical description you explained in so easy and smooth manner. This incredibly amazing. I also would love to share my home appliance partner expressrepair.ca, a fridge repair kitchener service that is dedicated to it's clients always.May be some guys here find it useful.

    ReplyDelete
  8. Motor winding resistances of the single door direct cooled refrigerator compressor is as below:
    Common - running = 29 ohm
    Common - starting =32 ohm
    Running-starting = 60 ohm
    Can we conclude that compressor ok?

    ReplyDelete
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