A sudden stop of the refrigerator is always stressful, because food supplies are at risk. Most often, unit owners immediately suspect a failure of the main system unit - compressor. It is this unit that is responsible for circulating the refrigerant and creating the necessary pressure in the circuit. However, before calling a technician or buying a new motor, it is worth carrying out initial diagnostics yourself.
Understanding how to check a refrigerator compressor will allow you to save a significant amount on diagnostics or even repair the equipment yourself. In some cases, the problem lies not in the motor itself, but in the start relay or wiring. A competent approach to the examination will help to accurately determine the source of the malfunction.
In this article we will analyze all available verification methods: from visual inspection to the use of measuring instruments. You will learn how to distinguish an interturn short circuit from a simple open circuit, and understand when repairs are really necessary.
Primary diagnostics: external signs of a malfunction
Before disassembling the housing and taking up tools, it is necessary to analyze the behavior of the refrigeration equipment. Often the symptoms of a breakdown are visible to the naked eye or audible. If compressor hums, but does not start, or works continuously, without turning off for hours, these are the first alarm bells.
Pay attention to the temperature of the motor housing. If it is so hot that it cannot be touched, this may indicate overheating of the windings or jamming of the mechanism. Smell is also an important indicator. The appearance of a strong smell of burning or scorched plastic indicates burnt insulation or melted start relay contacts.
⚠️ Attention: If you hear a loud click, followed by a hum, and after a few seconds another click and silence, this is a classic sign of an attempt to start a jammed motor or faulty relay. Do not try to connect the device to the network repeatedly in this mode.
Visual inspection of the wires can also provide answers. Look for blackened contacts, signs of oxidation, or mechanical damage to the insulation. Sometimes the reason is trivial - a loose power cord, which is easy to put back in place.
Required tool for checking the compressor
For high-quality diagnostics, you will need a minimum set of tools. Without them, the check will be superficial and may not give an accurate result. The main device is multimeter (tester), which allows you to measure the resistance of the windings and check the integrity of the circuit.
In addition to the electronic meter, you will need screwdrivers to dismantle the compressor casing and remove the start relay. Pliers for biting off the service tube (if a pressure test is required) and electrical tape for temporary isolation of contacts will not be superfluous.
- 🔧 Multimeter with continuity mode and resistance measurement (Ohm).
- 🔧 A set of screwdrivers (phillips and flat) for disassembling the unit.
- 🔧 Pliers or side cutters for working with wires.
- 🔧 Flashlight for illuminating hard-to-reach places in the compressor niche.
It is important that the measuring device is in working order and its battery is charged. A low-quality tester may show false resistance, leading to an erroneous diagnosis. Before starting work, make sure that the refrigerator is disconnected from the power supply.
Dismantling and access to the electrical part
To ring the compressor, you need gain access to his contact group. To do this, you need to move the refrigerator away from the wall and remove the back metal cover at the bottom of the case. Usually it is secured with several screws.
After removing the cover, you will see a black barrel-shaped element - this is it compressor. A plastic box is attached to the side or top of it - a starting relay. It is through it that power is supplied to the motor windings. Carefully remove this box, having previously photographed the location of the wires so as not to confuse the contacts during assembly.
On the motor housing you will see three contacts coming out of the sealed flask. They can be protected with an additional plastic cover. Your job is to provide clean access to these terminals for the multimeter probes. If there are oxides or carbon deposits on the contacts, they should be carefully cleaned.
⚠️ Attention: It is strictly forbidden to carry out any work to dismantle the relays and contacts while the refrigerator is plugged in. The risk of electric shock in the environment (condensation) is extremely high.
Sometimes access to the wires is difficult due to the design features of the model Indesit or Atlant. In such cases, it may be necessary to remove the entire compressor from the frame, but this is rarely required for an initial test.
Checking the starting relay for serviceability
Before sinning on the engine itself, it is necessary to rule out a malfunction of the starting relay. This small element often fails before the compressor winding burns out. The relay is responsible for sending an impulse to the starting winding at the moment of start.
Remove the relay and shake it near your ear. If a clear knocking or ringing sound is heard inside, this means that the contact group or core is loose. A working relay should be quiet. However, the absence of sound does not guarantee 100% serviceability, so it is better to carry out an electrical test.
Using a multimeter in resistance measurement mode, ring the relay contacts. The testing scheme depends on the type of device (electromagnetic or posistor). For electromagnetic relays, the coil resistance should be within normal limits (usually several tens of Ohms), and the contacts at rest should be open or closed depending on the design.
- 🔌 Visually inspect the relay body for cracks and melting.
- 🔌 Check the contacts for carbon deposits or oxidation.
- 🔌 Ring the coil circuit - the resistance should not be infinite.
- 🔌 Make sure that the posistor (if there is one) is not chipped or cracked.
If the relay is faulty, replacing it will cost much less than repair or replacement compressor. New relays are inexpensive and easy to install in place of the old ones.
How does the starting relay work?
When the refrigerator is turned on, current passes through the starting winding, creating a magnetic field. This field draws in the core, which closes the contacts of the working winding. When the engine picks up speed, the current drops, the core drops, and the starting winding is turned off. If this mechanism is broken, the motor hums but does not start.
Testing the compressor windings with a multimeter
This is the most important stage of diagnosis. There are usually three terminals located on the compressor contact group. They form a triangle. Two of them lead to the working and starting stator windings, and the third is the common output. The master’s task is to find the common contact and measure the resistance between all pairs.
Switch the multimeter to resistance measurement mode (limit 2 kOhm or 200 Ohm). First, find the common wire. The resistance between the working and starting terminals will be greatest. The resistance between general and working is average, and between general and starting is the smallest (or vice versa, depends on the circuit, but the sum of the two smaller ones should equal the larger one).
Normal resistance values vary depending on the power of the motor and the model (for example, Danfoss or Secop). Typically, the resistance of the working winding is 10–30 Ohms, and the starting winding is 20–40 Ohms. If the device shows one (infinity), it means there is an open circuit. If it shows zero, there is a short circuit.
It is also necessary to check the breakdown on the housing. Switch the tester to dialing mode (with sound). Touch any contact with one probe, and touch the cleaned area on the compressor housing (where there is no paint) with the other. The device should be silent. If there is a squeak or the readings creep down, it means the insulation is broken the motor is faulty.
☑️ Algorithm for checking the windings
The table below will help you navigate the obtained resistance values for various types of faults:
| Measurement type | Normal | Open circuit | Short circuit | Fault to housing |
|---|---|---|---|---|
| Multimeter readings | 10–60 Ohm (depending on the winding) | Unit (∞) or 0 (in Ohm mode) | Close to 0 Ohm | Squeak in dialing mode |
| Motor condition | Good | Winding burned out | Interturn short circuit | Dangerous to life |
Starting the compressor directly (without a relay)
If the electrical test of the windings showed normal, and the relay is working properly, but the refrigerator still does not work, you can try to start the compressor directly. This method allows you to eliminate any doubts about the performance of the motor.
To do this, you will need a piece of wire with a plug. One end is stripped and connected to the common contact, the other to the contact of the working winding (the one where the resistance was average). With this method, there is no need to connect the starting winding; a short-term impulse is sufficient, which can be created by quickly touching the contact of the starting winding with the wire from the plug (using extreme caution!).
⚠️ Attention: This method is dangerous! You work with 220V mains voltage on open contacts. You can only hold the wires by the insulation. If you are not confident in your skills, it is better to abandon this method.
If the motor hums and vibrates confidently when power is applied, it is working. The problem was in the relay or thermostat. If there is a quiet hum, a click and silence, the piston group may be jammed.
Diagnostics of mechanical faults
There are situations when The electrics are in order, the windings are intact, the relay clicks, but the refrigerator does not cool. In this case, the problem may be mechanical. The compressor may be “jammed” - the pistons are stuck to the cylinders due to oil production or overheating.
This can be determined by the characteristic sound: the engine is trying to start, it hums loudly, vibrates, but the shaft does not rotate. After a few seconds, the thermal protection is triggered and a shutdown click is heard. Repeated starts can finally finish off the motor.
There is a method of “wedging” by increasing the voltage or applying pressure in the opposite direction, but at home these methods are risky and often give a temporary effect. If the compressor is jammed, the most rational solution would be to replace it.
- 🛠 Check whether the relay is stuck in the closed position.
- 🛠 Feel the tubes: if one is hot and the other cold immediately after turning on, the compressor is working.
- 🛠 No vibration on the body of a running (by sound) motor indicates idling.
- 🛠 The presence of oil smudges around the compressor rod is a sign of depressurization of the seals.
It is also worth mentioning an interturn short circuit, which is difficult to detect with a conventional multimeter. It manifests itself in the fact that the resistance of the windings seems to be normal, but the motor consumes increased current and heats up quickly. For accurate diagnostics, current clamps are needed.
Is it possible to repair a burnt-out compressor at home?
Replacing the windings or overhauling the piston group at home is impossible. The compressor is a sealed unit that is sealed at the factory. Its repair requires special equipment for vacuuming and charging with freon, as well as high qualifications. In everyday life, only replacing the entire unit is available.
Why does a new compressor burn out after a few months?
A common reason is poor-quality installation. If the pipes were not properly soldered during installation, air or moisture could enter the system. It was also important to flush the system if the previous motor burned out, since oil combustion products could remain in the condenser and ruin the new unit.
How much does replacing a compressor cost compared to buying a new refrigerator?
The cost of a new compressor, including the work of a technician and consumables (freon, oil, filter drier) usually ranges from 30% up to 50% of the price of a new budget refrigerator. If the equipment is more than 10 years old, it is often more economically feasible to buy a new unit.
Is it dangerous to use a refrigerator with a faulty compressor?
If the compressor simply does not turn on, it is safe, the food will simply spoil. But if there is a breakdown in the case (even a weak one), the refrigerator case can be “pinched” by current. This is deadly. Freon leakage in a closed room is also dangerous, although modern refrigerants (R600a) are explosive only in high concentrations in the presence of a spark.