How to check the refrigerator compressor: video diagnostics and measurements

Refrigerator failure is always stressful, because the safety of food and comfort in the home are at risk. When the unit stops freezing or, conversely, works without stopping, the motor becomes the first suspicious element. It is possible to understand what exactly is broken without leaving home if you know the main signs of a malfunction and diagnostic methods. The video instructions in this article will help you visually master the verification process, and the text manual will provide the necessary technical details.

Before disassembling the equipment, you should listen to the sounds it makes. If the motor hums but does not start, or clicks and immediately stops, this is a sure sign of problems with the trigger mechanism or the very heart of the system. However, the final verdict can only be made after an instrumental check, which we will discuss in detail below. Self-diagnosis allows you to save time on calling a technician and understand exactly whether the repair is worth the money spent.

It is important to immediately note that working with electrical components requires compliance with basic safety rules. Before any manipulations inside the housing, it is necessary to completely de-energize the device by removing the plug from the socket. Ignoring this rule can lead to electric shock or damage to the electronic control boards.

Primary visual and auditory diagnostics

The check should begin with a simple inspection and analysis of the sound of the unit. Refrigeration compressor - this is a sealed unit, and its internal condition is often reflected in the external parameters. If you hear a steady hum followed by a clicking sound followed by silence, this indicates that the start relay is trying to start the engine but is unsuccessful. In such cases, the motor may either be mechanically jammed or have a break in the windings.

Pay attention to the temperature of the motor housing. If, after several attempts to start, the metal casing becomes scalding hot in a matter of seconds, this is a bad sign. Normal operating heating occurs gradually over 20-30 minutes of operation. Excessive heating in the first minutes often indicates an interturn short circuit or a wedge of the piston group.

⚠️ Attention: If you smell burning or see sparking in the area where the wires are connected, immediately stop trying to connect the device to the network. Further operation may lead to a fire in the wiring.

It is also worth checking the condition of the start relay, which is mounted on the side of the compressor. Often the problem lies in it, and not in the engine itself. If the relay makes a rattle sound when shaken, it means that the internal contact group is damaged and requires replacement. This is the most common and cheapest malfunction, simulating a motor breakdown.

A necessary tool for checking the motor

For high-quality diagnostics, you will need a minimum set of tools, which can be found in many home craftsmen. The key device is multimeter (tester), which allows you to measure the resistance of the windings and check the integrity of the circuit. Without this device, it is almost impossible to carry out an accurate diagnosis, since it is impossible to determine a wire break inside the sealed casing by eye.

In addition to the multimeter, you will need screwdrivers to remove the back cover and dismantle the compressor protective box. Some models, for example Indesit or Atlantmay require a ratchet wrench to unscrew the fasteners. Also, it will not be superfluous to use electrical tape and pliers to carefully disconnect the terminals.

If you plan to carry out a deeper check by flushing the system, you will need a nitrogen cylinder and a pressure gauge station, but this is not necessary for the initial check of the serviceability of the windings. A basic set is enough. It is important that the multimeter probes are in good working order and that the battery in the device is not discharged, otherwise the readings will be incorrect.

Checking the integrity of the windings with a multimeter

The most reliable way to find out the condition of the engine is to ring its windings. To do this, you need to remove the start relay and the protective cover, gaining access to the three contacts on the compressor terminals. They are usually arranged in a triangle. Switch the multimeter to resistance measurement mode (Ohms) to the limit of 200 Ohms or 2 kOhms.

You need to measure the resistance in pairs between all three contacts. Record the resulting values. Normal resistance values for a working household compressor are usually in the following ranges:

• 🔌 Between the working and starting contact: from 20 to 40 Ohm
• ⚙️ Between the working contact and the housing: infinity (gap)
• 🔥 Between the starting contact and body: infinity (break)
• 🔋 Total resistance of the main and starting windings

If the device shows one (infinity) between any two terminals of the windings, it means in the circuit break. This may be due to the burnout of the wire inside the coil or burnout of the contact on the internal comb. In this case, the compressor cannot be repaired at home and requires replacement.

⚠️ Attention: Never check the resistance of the windings while the compressor is connected to the network or the capacitor is not discharged. This is guaranteed to disable your measuring device.

Pay special attention to checking for breakdown on the housing. One probe is applied to any of the three contacts, and the second is applied to a cleaned area on the metal body of the motor (you can slightly scratch the paint for better contact). If the multimeter shows at least some resistance, it means that the insulation is broken and the motor is shorting. Operating such a unit is deadly.

Why is it important to clean the housing during inspection?

The paint that covers the compressor is a dielectric. If you simply apply the probe to a painted surface, the device will show an open circuit even if there is a breakdown. A small stripping down to the metal guarantees measurement accuracy and safety.

Analysis of the operation of the starting relay

Often the reason that the refrigerator does not turn on is not the motor itself, but starting relay. This small block is responsible for supplying a starting pulse and turning off the starting winding after the rotor accelerates. If the relay is faulty, the motor will hum, trying to start, but the shaft will not rotate.

Checking the relay begins with a visual inspection. There should be no cracks, traces of soot or melting on the plastic case. There should be no loose parts inside. If you hear a knock when shaking, it means the contact group is damaged. In a relay with a posistor (ceramic element), the heating element itself can also burn out, which is not always visually noticeable.

To accurately check the relay, you need to ring it with a multimeter:

• 🔍 Check the inductance coil for a break
• 🔥 Make sure the contacts are not shorted short in a cold state (for some types)
• 🔄 Check the mobility of the contacts (if the relay is electromagnetic)

If the relay is working properly, but the motor still does not start, the problem is most likely in the compressor itself. However, before drawing final conclusions, it is worth checking the current consumption. To do this, you will need current clamps, which are placed on the power cord when the device is turned on. If the current sharply jumps to maximum values ​​and knocks out the machine, it means that there is an interturn short circuit in the windings turn-to-turn short circuit.

Table of typical faults and symptoms

To systematize the data obtained, it is convenient to use a summary table. It will help compare symptoms, instrument readings and the probable cause of the breakdown. This will speed up the process of making a decision to repair or replace the unit.

As can be seen from the table, in most cases, when it comes to internal damage to the windings (break, short circuit, breakdown), repairing the compressor itself is impossible. The sealed housing does not allow replacing a burnt out winding without special factory equipment. Therefore, diagnosis often leads to the conclusion that it is necessary to purchase a new unit or an expensive replacement of the motor with refilling with freon.

Direct start of the compressor (Test without relay)

There is a method for checking the performance of the motor by applying voltage directly, bypassing the standard relay. This method allows you to understand whether the engine is able to rotate at all. However, it should be used with extreme caution and only at your own peril and risk.

To implement this method, you will need a piece of wire with a plug and a button (or just neatly twisted contacts). The circuit is simple: phase and zero are supplied to the working contacts, and the starting pulse is supplied briefly. If the motor is working properly, it should start and begin pumping air confidently. If there is a hum and a click, but there is no rotation, the motor is jammed.

⚠️ Attention: Direct connection puts a heavy load on the network. Make sure the wiring can handle the inrush current. It is strictly forbidden to hold the start button for more than 2-3 seconds - the winding will burn out.

If the compressor starts, but is very loud or heats up faster than usual, this indicates that the mechanical part is worn out. The bearings may have worn out, or the piston group may have been damaged. In the long term, such a motor will still have to be changed, since it will create an extra load on the system and can lead to depressurization of the circuit.

When a compressor replacement is necessary

When deciding on a replacement, you need to take into account not only the cost of the motor itself, but also the cost of the work. Replacing a compressor is a complex process that includes opening the circuit, soldering a new unit, evacuating the system and charging with refrigerant. It is impossible to carry out this work independently without equipment.

If the diagnostics showed a break, a breakdown in the body or a wedge, it is more economically feasible to consider purchasing a new refrigerator, especially if the current model is more than 7-10 years old. Older models are less energy efficient, and repair costs can be up to 60% of the cost of a new device.

If you decide to change the motor, choose original spare parts or proven analogues from manufacturers like Secop (formerly Danfoss), Embraco or LG. Cheap Chinese copies often do not last long and can repeatedly damage the cooling system.

Is it possible to install a compressor of higher power?

Theoretically, it is possible if the mounting dimensions and type of refrigerant match. However, a more powerful motor will cool the evaporator faster, which can lead to frequent on/off or, conversely, operation without shutting off if the thermostat does not have time to react. It’s better to stick to original specs.

Why does the compressor heat up to 90 degrees?

The temperature of the housing of a working compressor can reach 80-90 degrees Celsius, and this is normal. The metal casing serves as a radiator that removes heat generated by freon compression and friction of mechanical parts. You should be concerned if heating occurs instantly (in 10-20 seconds) or if the temperature is so high that plastic nearby melts.

Is it possible to restore a jammed compressor?

There is a “folk” method of resuscitating a jammed motor by applying 220V voltage through a powerful lamp or transformer for a short time to tear him out of his place. However, the success rate of this method is less than 10%, and the risk of permanently finishing off the windings or damaging the valves is very high. In modern hermetic compressors, this method practically does not work.

A knock is heard inside the compressor, what should you do?

A knock inside the hermetic unit indicates mechanical destruction of the motor suspension or damage to the valves. The springs on which the electric motor is suspended inside the casing could burst or jump off. Broken bearings can also knock. Such a compressor will operate very noisily and for a short time. The only solution is replacement.

What resistance is considered normal for different brands?

Resistance standards may vary slightly. Refrigerators Atlant and Indesit are characterized by values ​​of 20-25 Ohms for the working winding. For LG and Samsung with inverter systems, diagnostics are carried out differently, through the control board, and it will not be possible to check them “head-on” with a conventional multimeter. There you need to look for errors on the display.