How to check the compressor on the refrigerator using a multimeter, tester, pressure gauge


A refrig­er­a­tor is made up of many parts, but the main ele­ment is the com­pres­sor. The qual­i­ty of the work of this house­hold appli­ance depends on its ser­vice­abil­i­ty. When the refrig­er­a­tor is not work­ing, the first thing to check is the com­pres­sor. In this case, it is not nec­es­sary to imme­di­ate­ly go to the ser­vice cen­ter, since you can do the work at home. How exact­ly to check the health of the com­pres­sor, we will con­sid­er fur­ther.

How is a compressor arranged?

Turn­ing the refrig­er­a­tor, on the reverse side we will see a cas­ing, which is a pro­tec­tive ele­ment for the com­pres­sor. The unit itself is locat­ed inside the cas­ing — it is fixed in lim­bo. The com­pres­sor was with­out fail cov­ered with spe­cial oil.


The device of house­hold refrig­er­a­tors is prac­ti­cal­ly the same in all mod­els, both old and new. The com­pres­sor is a pis­ton elec­tric motor, a relay, a work­ing and start­ing wind­ing. The per­for­mance of the unit depends on the alter­nat­ing cur­rent. If you’re new to elec­tric motors, the best com­par­i­son would be an engine from a sin­gle-cylin­der car.

The refrig­er­a­tor works accord­ing to this scheme: a low tem­per­a­ture inside is formed due to the refrig­er­ant, which is in a vapor state. Due to the com­pres­sion (pres­sure) from the oper­a­tion of the elec­tric motor, the refrig­er­ant set­tles into a spe­cial con­tain­er and turns into a liq­uid.

Pay atten­tion to the refrig­er­a­tor com­pres­sor dia­gram:

Compressor diagram

Of course, if the motor does not work, then the whole sys­tem will not func­tion. There are three out­puts from the body of the unit. Even with­out open­ing the cas­ing, you will see pro­trud­ing bay­o­nets that form a tri­an­gle at the bot­tom:

  • The first con­clu­sion is gen­er­al;
  • The sec­ond comes from the work­ing wind­ing;
  • The third comes from the start­ing wind­ing.

In the lat­est mod­els, in addi­tion to the above ele­ments, a “gear­box” can be installed, which reg­u­lates the speed of the elec­tric motor.

Checking with a multimeter (tester): step by step instructions

To check the com­pres­sor using a mul­ti­me­ter (tester), fol­low these steps:

  1. The cas­ing is dis­man­tled, and then the unit itself is removed from there. We need to remove the relay — it is held by a pro­tec­tive cov­er.
  2. The resis­tance is mea­sured using the through con­tacts with a tester. If the com­pres­sor from the refrig­er­a­tor is work­ing prop­er­ly, then there should be a resis­tance of 20 ohms between the left and top con­tacts, about 15 ohms between the top right, and 30 ohms between the left and right con­tacts.
  3. If the mul­ti­me­ter gives oth­er read­ings, then the unit is mal­func­tion­ing. Depend­ing on the mod­el of the refrig­er­a­tor and the elec­tric motor itself, the indi­ca­tors may be dif­fer­ent, but the num­bers do not change by more than 5 ohms.
  4. Next, check the resis­tance between the cas­ing and the lead wires. One tester probe should be con­nect­ed to one of the fit­tings (you need to select the cop­per part), and the sec­ond to the through con­tacts. In the case when the unit is work­ing, the mul­ti­me­ter will show an open on the dis­play. If resis­tance appears instead, then there is a seri­ous mal­func­tion in the motor.

In the fol­low­ing arti­cle, you will learn more about how to use a mul­ti­me­ter.

Compressor check

Read also:

Checking with a pressure gauge

Let’s say that the check showed no defects, but the refrig­er­a­tor does not work. In this case, you need a pres­sure gauge with which you can mea­sure the pres­sure. It is nec­es­sary to con­nect a hose with a branch (sim­u­la­tor) to the dis­charge fit­ting and take read­ings with the com­pres­sor run­ning. If the indi­ca­tor on the dis­play is 6 atmos­pheres, while the fig­ure is grow­ing, then the refrig­er­a­tor is work­ing prop­er­ly.

If you have an old but work­ing refrig­er­a­tor at home, then you can take an elec­tric motor from it. The relay on old­er mod­els quick­ly fails, but you can con­nect the com­pres­sor with­out it, that is, direct­ly. To do this, you will have to con­nect the wind­ings.

Atten­tion! This work is dan­ger­ous, as it can not only dam­age the appli­ances, but also harm your health. It is worth mak­ing a con­nec­tion with­out a reg­u­lat­ing ele­ment only if an expe­ri­enced repair­man is engaged in this work.

Current test

It is also rec­om­mend­ed to check if the cur­rent reach­es the motor. In this case, you will need a work­ing relay. It is bet­ter to take a new device that has been test­ed before.

The relay must be con­nect­ed to the com­pres­sor and run. Here the tester will help us again, only in this case it should be with ticks. It is nec­es­sary to take one of the net­work wires and clamp it with tongs. If the dis­play reads 1.3 A and your motor pow­er is 140 W, then the cur­rent flows prop­er­ly. With less pow­er, the cur­rent strength should also be less. For exam­ple, when mea­sur­ing an engine at 120 W, the indi­ca­tor on the mul­ti­me­ter should be 1.1–1.2 A.

Most often, it is the relay that fails in the unit, so first of all you need to test this ele­ment. In this case, the same method is used as when check­ing the refrig­er­a­tor com­pres­sor with a mul­ti­me­ter.

Video instruction on how to check the refrigerator compressor

Know­ing how to test a refrig­er­a­tor com­pres­sor in the­o­ry is good, but you also need to see the process itself. To do this, watch this video, where the wiz­ard describes in detail check­ing the refrig­er­a­tor with a tester and in oth­er ways.

Now you know how to check the refrig­er­a­tor com­pres­sor your­self. You will be able to do this job if you have already dealt with elec­tri­cal repairs and know how to use a mul­ti­me­ter. Do not take on test­ing if this is your first expe­ri­ence. The right deci­sion would be to call a pro­fes­sion­al, espe­cial­ly if the refrig­er­a­tor is under war­ran­ty.





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