Wednesday, November 2, 2016

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 refrigerator or fridge compressor we have a electric induction motor which rotate the pump. In fridge compressor mostly in rated in single phase which have 3 terminals. i already publish a post about the start, run and common identification guide on this blog.
Some time when our refrigerator compressor stop working or not running problem then we must called a professional to test compressor or refrigerator. But if you want to check your compressor him self then this post is for you.

In this post i am telling you about some main and common reason of compressor not working and about testing compressor methods. There are many problems which we face in electrical refrigeration system and due which or refrigerator or Air conditioner stop working. But this post specially 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 instill a single phase motor which consist two types of winding which we called main winding (ruining winding) and Auxiliary winding (starting winding). But if the compressor have receiving the power supply and still not working or running then may be it's 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 gave an example of 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 our that which one terminal is common, start and run. The common terminal will be connect to overload protector or connect direct to electric supply wire. (note that direct wire was connected in those single phase compressor, in which the overload protector is instill internally).

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

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

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

  • Now if you find our the connectivity of winding and body then it's 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 it's resistance between one another. Test the compressor by unsung 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 same as in the above post then your compressor winding is not burn or if it's shown different reading between common, start and run then your compressor winding is burn.

  • Now if compressor winding resistance shown same as i 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 upper side then left side will be start and right hand side will run terminal, and danfoss compressors in which the common terminal on down side the right side will be start terminal and left side will be run as i 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 air conditioner compressor we have label 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, terminal of air conditioner compressor terminal is connect to 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 connect to capacitor and to compressor terminal will be your run terminal, mostly in split unit AC the blue color wire is use for run terminal. And the other wire will be your start terminal which will be connect to capacitor. Mostly this red color wire used for start terminal connection.

  • Now set the multi meter on ohm or resistance tasting or use a ohm meter and check the compressor, follow the same method as we use for fridge compressor terminal. However lets see the example.

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

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

  • Now test the compressor shortage between compr.... terminals with compressor body like fridge compressor and if the meter shown no reading then compressor winding is not shortage with body and if it's shown the reading then it's means that compressor windings is 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 that overload protector is connect to main terminal of compressor in series and if compressor overload protector stop working or internally open, the compressor is also stop working. However these are simple methods for checking compressor windings of single phase and now if you have any question then you can use the below comments section.


  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.

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

  3. Very usefull and good educational Post by you.

  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.