How to check if the refrigerator compressor is working

The lack of cold in the chambers or, conversely, excessive freezing of products often indicates problems with the core of the cooling system - the motor. Owners of household appliances Indesit, Atlant or Bosch face the need for quick diagnostics in order to understand whether complex repairs are required or whether it is enough to replace a small part. If your refrigerator stops freezing, but the light inside is on, the first thing you should do is listen to the sounds it makes.

Modern units operate quite quietly, so any extraneous hum, clicks or complete silence should alert you. Compressor is The unit is expensive and replacing it is often comparable in cost to purchasing a new device, so accurate diagnosis is critical. Do not rush to call a specialist if you have basic skills in working with power tools and understand the principles of electrical safety.

In this article we will analyze in detail the algorithm of actions that will allow you to independently determine the health of the engine. You will learn how to distinguish a breakdown of the motor itself from a failure of the starting relay or thermostat. Correct diagnostics will save you time and money, allowing you to make an informed decision on further actions.

⚠️ Attention: Carry out any work on checking the electrical circuits of the refrigerator only with the device completely disconnected from the network. Electric shock can be fatal.

Primary visual and acoustic diagnostics

The first stage is always an external inspection and analysis of the sound of the equipment. Go to the refrigerator and listen carefully: if you hear a low hum that ends abruptly with a click, this is a classic symptom of a restart attempt. The engine tries to start, but something prevents it from gaining momentum. In normal operation, engine should start smoothly and operate cyclically, turning on and off at certain intervals.

Pay attention to the temperature of the motor housing. If it is hot to the touch, but the chambers are not cooling, this may indicate that the unit is running dry or jammed. Also inspect the rear wall: the presence of oily stains or smudges in the lower part where the compressor is located often indicates a depressurization of the system. In this case, checking the electrical system may be useless, since the problem lies in a leak of refrigerant.

If there is visually no damage to the wire insulation or obvious traces of oil, you can proceed to a more in-depth analysis. Often the cause of failure is not the motor itself, but auxiliary elements such as a thermostat or a start-up relay. Understanding how yours behaves in different modes will help narrow down the troubleshooting. refrigerator in different modes, will help narrow down the troubleshooting area.

Checking the start relay and thermostat

Before “climbing” into the compressor itself, it is necessary to eliminate malfunction of the control circuits. The starting relay is responsible for supplying voltage to the motor windings at the moment of start. If it burns out, the motor simply will not receive an impulse to start. Remove the plastic casing from the side or bottom of the compressor (depending on the model, for example, the design may differ) and remove the relay. Visually inspect the contacts for carbon deposits or melting. If the relay is electromagnetic, you can gently shake it near your ear: the presence of a rattling sound inside indicates destruction of the core or contacts. The thermostat also plays a key role: if its contacts are oxidized or “stuck,” the circuit will not close and voltage will not flow to Liebherr or Stinol design may vary) and remove the relay.

Visually inspect the contacts for carbon deposits or melting. If the relay is electromagnetic, you can gently shake it near your ear: the presence of a rattling sound inside indicates destruction of the core or contacts. The thermostat also plays a key role: if its contacts are oxidized or “stuck,” the circuit will not close and the voltage will not flow the unit.

• 🔌 Disconnect the wires from the relay and test them with a multimeter for circuit integrity.
• 🔍 Inspect the inside of the relay for traces of burning or soot.
• ⚙️ Check the thermostat rod: it should move freely and click when the temperature changes.

Nuances of checking different types of relays

Relays can be electromagnetic and posistor. PTC (often found in models Samsung i LG) do not rattle when shaken. They are checked exclusively by continuity: in a cold state the resistance should be low, when heated it should go to infinity. If the posistor “rings” and is hot, it is broken.

If after replacing or checking the relay the situation has not changed and the motor still does not start, we proceed to directly checking the electrical parameters of the compressor itself. This requires greater caution and the presence of a measuring device.

Instrumental testing of windings with a multimeter

To carry out high-quality diagnostics, you will need a multimeter (tester). Switch the device to resistance measurement mode (Ohms). On the compressor housing you will find three terminals, usually arranged in a triangle. Remove the start relay to access them. Your task is to measure the resistance between each pair of contacts.

Normal resistance values ​​depend on the power of the motor, but usually they are in the range of 10 to 30 ohms for the starting winding and from 15 to 35 ohms for 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 (between the working and starting terminals). If the multimeter shows “infinity” (one on the screen or the arrow does not deviate), this means break windings.

Pay special attention to checking for insulation breakdown. Press one multimeter probe to any of the three contacts, and the second to a place on the compressor housing that has been cleared of paint (metal tube or housing). The device should show infinite resistance. If you see any values ​​(even large ones), it means that something has happened short circuit to the case, and it is dangerous to operate such a refrigerator.

⚠️ Attention: If the multimeter shows a resistance close to zero between the windings, this indicates an interturn short circuit. Such a compressor can only be replaced, it cannot be repaired.

Measuring the current strength when starting the engine

If checking the resistance of the windings does not reveal obvious breaks or short circuits, but the motor still does not start or knocks out the circuit breaker, it is necessary to measure the strength of the starting current. To do this you will need current clamps. This method allows you to understand whether the motor is consuming current and whether it is mechanically jammed.

Connect the refrigerator to the network through a current clamp, covering one of the power wires (phase or neutral). At the moment of startup, a working compressor consumes a current that is 3-5 times higher than the rated operating current. For example, if the operating current is 1 Ampere, the starting current can reach 3-5 Amperes. If the current sharply jumps to the maximum and immediately drops to zero (a relay click is heard), it means that the engine is trying to start, but cannot turn over.

• 📉 Low current when humming indicates that the rotor cannot move (jamming).
• 📈 Excessively high current indicates inter-turn short circuit, which was not detected during testing.
• ✅ A normal starting pulse followed by a decrease to operating values indicates the serviceability of the electrical part.

Constant humming without switching to operating mode and subsequent shutdown due to overload is a sure sign of mechanical failure inside the compressor or critical wear of the rubbing pairs. In this case, further operation will only lead to overheating of the wiring.

Diagnostics of mechanical faults and jamming

The mechanical part of the compressor is a piston group that compresses the gas. Over time, the rubbing parts wear out, the oil thickens or loses its properties, which leads to the piston jamming. If the electrical part is intact (the windings are intact, the current is flowing), but the shaft does not rotate, most likely a “wedge” has occurred.

There is a “swinging” method, which sometimes allows you to revive a jammed compressor, although this is a temporary measure. The idea is to apply voltage directly to the operating winding, bypassing the starting relay, often using a capacitor to create starting torque. However, this method requires high qualifications and carries risks.

Signs of mechanical wear or damage to the valves:

• 🔨 Metallic knocking or clanging inside the motor housing during operation.
• 💨 The compressor works, but does not create pressure (the tubes at the outlet and inlet have the same temperature).
• 🌡️ There is no temperature difference between the condenser (rear grill) and the evaporator.

⚠️ Attention: Opening the compressor housing for mechanical repairs at home is impossible and impractical. Violation of the factory seal requires evacuation of the system and charging with freon, which requires expensive equipment.

Symptoms of interturn short circuit of windings

One ​​of the most insidious problems is interturn short circuit. It may not appear when measuring resistance with a conventional multimeter, since the resistance changes slightly. However, when voltage is applied, such windings begin to overheat and consume excess current.

The main symptom is the rapid and strong heating of the compressor housing in just a few minutes of operation. In this case, the refrigerator may even begin to freeze, but very soon the thermal protection relay will operate and the unit will turn off. After some time, having cooled down, it will turn on again and the cycle will repeat. This phenomenon is called “clocking.”

This malfunction can be accurately diagnosed only using a special device that measures the inductance of the windings, or by the method of exclusion. If all external elements (relay, thermostat) are in good working order, and the motor behaves in the manner described above, most likely its life is exhausted due to a violation of the insulation of the turns.

Frequent questions and answers (FAQ)

Is it possible to replace the compressor yourself without experience?

Theoretically, it is possible, if you know how to solder copper pipes and have access to a vacuum pump and a cylinder of freon. However, the process requires precise calculation of the amount of refrigerant and oil. Without special equipment, it will not be possible to recharge the system efficiently, so for most users, replacing the compressor is a task for the service center.

Why may a new compressor not start?

A common reason is the installation of an inappropriate starting relay or an error when connecting wires to the terminals. Also, a new unit may be defective, although this rarely happens. Be sure to check the compliance of the relay model and the connection diagram.

How long does a refrigerator compressor last on average?

The service life of modern compressors, especially inverter types (found in LG, Hitachi), is 10-15 years or more. Conventional piston motors last about 7-10 years, depending on the intensity of use and the quality of the electrical network.

Is it dangerous to use a refrigerator with a faulty compressor?

If the compressor hums but does not start, it consumes a large starting current, which can lead to overheating of the refrigerator wiring and a fire. If it simply does not turn on due to a break in the winding, there is no danger other than damage to the food.