The situation when the refrigerator stops freezing, and the food inside quickly deteriorates, always takes you by surprise. The first suspicion is the failure of the motor-compressor, which is the “heart” of the entire cooling system. Understanding how to check a refrigerator compressorallows you not only to save on calling a technician, but also to accurately determine whether the unit can be repaired or whether it is easier to purchase a new one.
However, you should not immediately panic and disassemble the equipment if it simply stops humming. Often the reason lies in less significant components, such as a thermostat or start relay. In this article, we will analyze in detail the algorithm of actions that will help you independently carry out initial diagnostics and identify the true culprit of the breakdown without unnecessary haste.
Visual inspection and primary signs of malfunction
Before taking up the tools, it is necessary to conduct a thorough external inspection of the rear part of the unit. This is where the compressor is located, and often visual defects speak louder than any words about the problem. If you notice oily spots on the tubes or the motor housing itself, this is a sure sign of depressurization of the system, which requires professional intervention.
Pay attention to the condition of the wiring and contacts. Melted areas or a characteristic burning smell indicate that starting relay or the motor windings have overheated. Also an important indicator is the temperature of the case: if the motor is cold when the refrigerator is plugged in, it may not start due to lack of power, and if it is hot to the point where it is impossible to touch, the piston group may be jammed.
⚠️ Attention: If when you turn on the refrigerator you hear a loud click, followed by silence follows, and this is repeated cyclically - this is a classic symptom of an attempt to start a jammed engine or a faulty start relay.
Listen to the sounds that the equipment makes. Normal operation is accompanied by a uniform hum. Unusual knocking, clanging, or metallic grinding noises indicate mechanical wear on internal parts such as valves or bearings. In such cases, further operation may lead to complete destruction of the compressor.
Checking the thermostat and electrical circuit
Before sinning on the motor, make sure that the start signal is received at all. Often the problem is trivial: a faulty thermostat temperature sensor that simply does not give the command to turn on. To check, you can close the contacts of the thermostat (after disconnecting the refrigerator from the network), but it is safer to use a multimeter in dial mode.
If the thermostat is working, the power circuit should be intact. Check the integrity of the power cord and plug. Inside the housing, in the area where the compressor is connected, inspect the terminal block. Oxidized contacts can create high resistance, due to which there is not enough voltage to start the engine.
It is important to understand the difference between no voltage and no start. If 220 volts comes to the motor terminals, but it is silent, the problem is in it or in the starting device. If there is no voltage, look for the cause in the control circuit: control module, thermostat or wiring.
Diagnostics of the starting relay and capacitor
One of the most common reasons why the compressor does not start is the failure of the starting relay. This small block is responsible for sending an impulse to the starting winding. To check it, you need to remove the relay from the compressor contacts and shake it: if a ringing or knocking sound is heard inside, it means that the mechanical part (core) is damaged or jammed.
Visually inspect the insides of the relay. Blackened contacts, traces of carbon deposits or melted plastic indicate that the device was operating in emergency mode. In models with capacitor start, the capacitance of the capacitor is also checked. Bloating of the housing or leakage of electrolyte is a clear reason for replacement.
Replacing a relay is a simple procedure, but requires selection of the exact model. Universal relays may not be suitable for the operating current, which will lead to repeated breakdown or burning of the motor windings. Always check the markings with the old part.
⚠️ Attention: Some modern refrigerators are equipped with inverter compressors that do not have a classic start relay. In such systems, the start-up is controlled by an electronic unit, and simply replacing parts will not help here.
Checking the compressor windings with a multimeter
If the external elements are in good condition, then comes the turn of the most important part - checking the integrity of the electric motor windings. To do this you will need multimeter. Remove the protective cover and reach the three contacts on the compressor. They are usually arranged in a triangle.
Switch the device to resistance measurement mode (Ohms). You need to “ring” the contacts in pairs. For a working motor, the resistance between any two contacts should be in the range from 10 to 30 Ohms (for the starting winding) and from 15 to 50 Ohms (for the working winding). The exact values depend on the model and power motor.
If the device shows infinity (open) or zero (short circuit) between any contacts, the compressor is faulty. It is also critical to check the breakdown on the housing. Touch one probe to the bare metal of the case (where there is no paint), and the other to any contact. The device should be silent. Any resistance reading or sound signal means that the insulation is broken.
Table of normal resistance values
Usually the starting winding has a higher resistance than the working winding. The sum of the resistances of the two windings should be approximately equal to the resistance of the third pair of contacts (if the circuit allows such a measurement). It is better to look for accurate data in the technical documentation for a specific refrigerator model.
Measurement results should be written down so as not to get confused. If you find a break or short circuit, repairing the compressor at home is impossible - you need to rewind or replace the entire unit.
Analysis of operation under load and current measurement
More accurate diagnostics can be carried out by measuring the current consumption of the compressor during operation. For this, an ammeter or a multimeter with a current clamp is used. Measurements are taken on the wire going to the compressor at the time of startup and operation.
The table below shows approximate current values for various types of compressors. Exceeding these values indicates an overload, and too low a current indicates idle operation (for example, with a freon leak or valve problems).
| Compressor type | Power, W | Normal current, A | Starting current, A |
|---|---|---|---|
| Low-power (single-chamber) | 100-140 | 0.3 - 0.5 | up to 2.0 |
| Medium power (double-chamber) | 150-200 | 0.5 - 0.7 | up to 2.5 |
| High power (No Frost) | 220-300 | 0.7 - 1.0 | up to 3.5 |
| Inverter | Varies | 0.2 - 0.8 | Floating |
If the current consumption is significantly higher than normal, the compressor operates “at the limit”, which often happens when jammed or working in a vacuum (if the system is empty). In this case, the thermal protection relay will constantly turn off the engine, preventing it from gaining speed.
Mechanical faults and jamming
When the electrical part is working, but the motor does not turn, there is a high probability of mechanical jamming. Pistons can stick to the cylinders due to overheating or lack of lubrication. In some cases, the so-called “increased voltage supply method” helps, but it is dangerous and requires special equipment.
There is a less risky method - trying to wedge the compressor by applying voltage directly to the working winding (bypassing the starting winding) for a short time. However, this method requires extreme caution and awareness of the risks. If the motor does not move in 3-5 seconds, further attempts may finally finish off the windings.
Often the cause of knocking and noise is not the pistons themselves, but the valves. If the compressor hums, but does not create pressure in the system (the outlet pipes are cold or barely warm, but the inside is warm), then the valve group is leaky. This requires opening the compressor, which is practically impossible to do efficiently in everyday conditions.
⚠️ Attention: Opening the compressor housing breaks the tightness of the system. After any intervention in the tubes, professional evacuation and refrigerant charging will be required. You cannot simply “change the compressor” without charging freon.
When you need to call a specialist
Despite the possibility of self-diagnosis, there are situations when you cannot do without a specialist. If you find a break in the windings, a breakdown in the housing or mechanical jamming, the unit needs to be replaced. This process involves welding pipes, evacuation of the system and precise charging with refrigerant.
Also, professional help is needed if the refrigerator is working but not freezing, and the compressor is working properly. The problem may be a clogged capillary tube or a freon leak. These defects require special equipment to find and eliminate.
Do not ignore warranty obligations. If the refrigerator is under warranty, any DIY repairs or even removing seals from the compressor will void the warranty status. In such cases, the only correct solution is to contact an authorized service center.
Frequently asked questions (FAQ)
Is it possible to repair a burnt-out compressor yourself?
Theoretically, it is possible to rewind the windings, but in practice this is not economically feasible. The cost of work and materials often exceeds the price of a new compressor, and the quality and durability of such repairs are questionable. It is easier and more reliable to replace the entire assembly.
Why does the compressor turn on and then immediately turn off?
This is a thermal protection relay that is triggered. Reasons: malfunction of the starting relay, engine jamming, lack of refrigerant in the system (the motor overheats due to lack of cooling effect of freon) or problems with the electrical network (low voltage).
How much does it cost to replace a compressor?
The price consists of the cost of the unit itself (from 3 to 10 thousand rubles per depending on the model) and the cost of the master’s work (from 2 to 5 thousand rubles). The exact amount can be found out only after diagnosing a specific refrigerator model.
Does a working compressor hum?
Yes, a working compressor makes a smooth, monotonous hum. However, it should not be too loud, intermittent, or accompanied by a metallic clanging sound. The noise level depends on the type of compressor (regular or inverter) and the quality of installation of the refrigerator.