A sudden stop in the operation of the refrigerator often becomes an unpleasant surprise, especially when there are perishable foods inside. The first thing owners begin to suspect is the compressor, since it is this unit that is responsible for the circulation of the refrigerant. However, before calling a technician or buying new equipment, it makes sense to conduct an initial diagnosis. Checking the compressor This is a process that can be performed independently if you have a minimum set of tools and basic knowledge about the design of electrical appliances.
Understanding the principle of operation of the motor allows you to avoid unnecessary expenses and quickly determine the nature of the breakdown. Modern units from brands Indesit, Atlant or Beko have a similar engine design, which simplifies troubleshooting. In this article we will analyze a step-by-step algorithm of actions that will help identify the problem.
It should immediately be noted that any work related to electricity requires strict adherence to safety precautions. If you are not confident in your abilities or see clear signs of damage to the wiring, it is better to contact a professional. However, for those who are willing to take a risk and save on calling a specialist, detailed instructions are provided below.
Primary visual diagnostics and preparation
Before taking up the tools, it is necessary to conduct an external inspection of the unit. Often the reason for inoperability lies in a simple lack of power or damage to the power cord. Make sure the outlet is working by connecting another device to it. It is also worth checking whether the motor housing has overheated - if it is hot and the refrigerator is silent, the thermal protection relay may have tripped.
To carry out a more in-depth check, you will need to remove the back panel of the refrigerator. It is usually secured with screws that can be easily unscrewed with a Phillips screwdriver. After removing the casing, access to the compressor, capacitor and start relay will open. Carefully inspect the contacts for oxidation, blackening or melting.
⚠️ Attention: Before starting any work, be sure to disconnect the refrigerator from the power supply! Unplug the plug from the socket and wait 5-10 minutes for the capacitors to discharge and the residual voltage to subside.
Pay special attention to the condition of the tubes and soldering areas. If you notice traces of oil or a characteristic burning smell, this may indicate a depressurization of the system or an interturn short circuit. In such cases, further checking the electrical part may be pointless, since the problem lies deeper.
Necessary tools for testing
For high-quality diagnostics you will need a basic kit for a home technician. The main tool will be a multimeter (tester), which will allow 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 accurate diagnostics, since it is impossible to determine the condition of the windings “by eye.”
In addition to the multimeter, prepare the following tools:
- 🔧 Screwdrivers (Phillips and flat) for dismantling panels and terminals.
- 🔨 Pliers for carefully removing the terminal blocks.
- 🧤 Dielectric gloves to protect your hands when working with electricity.
- 🔦 Flashlight for illuminating hard-to-reach places in the rear niche.
If you plan to check the pressure or refill freon, the list of tools will expand, but for the initial check of the electrics this kit enough. It is important that the multimeter probes are in good working order, and that the device itself shows zero when the probes are shorted to each other.
Some compressor models, for example, inverter ones from LG or Samsung, require more complex diagnostics using specialized testers. For standard linear motors, a conventional analog or digital tester is sufficient. The main thing is to set the measurement range correctly.
Checking the serviceability of the starting relay
The failure of the starting relay is often mistaken for a compressor malfunction. This small block is responsible for supplying a starting pulse to the motor winding. If the relay is faulty, the engine may hum but not start, or may not make any sounds at all. The check begins with this element, since it is simpler and cheaper.
Remove the relay from the compressor. It is usually fixed on three contacts and held in place by spring clips or screws. Carefully disconnect it, first remembering or photographing the position of the wires. Shake the relay near your ear: if you hear a ringing inside, it means that the ceramic core is broken or the contact has broken off, and the part must be replaced.
How does the start relay work?
When turned on, the refrigerator consumes a large current. The starting relay (often a posistor type) heats up and opens the circuit of the starting winding, leaving only the main winding to work. If this process is disrupted, the motor cannot start.
To check the integrity of the contacts, use a multimeter in continuity mode. The resistance between the contacts should be either zero (closed) or infinite (open) depending on the type of relay and its position. If the meter shows average values or "jumping" numbers, the relay is faulty.
⚠️ Attention: Never try to start the compressor directly, bypassing the relay and thermal protection, for more than 3-5 seconds. This can lead to burnout of the windings and a fire.
If the relay is working properly, but the compressor does not start, the problem may be in the motor itself or in the supply wiring. Replacing the relay is a frequent and inexpensive repair that extends the life of the equipment. Make sure that the new relay matches the markings of the old one.
Diagnostics of motor windings with a multimeter
The most reliable way to check the condition of the motor is to measure the resistance of the windings. To do this, you need to remove the protective casing from the contact group of the compressor. You will see three contacts arranged in a triangle. Usually they are marked, but if there is no marking, you need to determine them experimentally.
Take a multimeter and switch it to resistance measurement mode (Ohm). Measure the resistance between each pair of contacts. Write down the results. The sum of the resistances of the two smaller values must equal the largest value. This is the resistance between the main contacts.
☑️ Algorithm for checking the windings
Normal resistance values depend on the motor power, but are usually within the following limits:
- 📏 Between the starting and operating windings: 15–45 Ohm.
- 📏 Between the working winding and the housing: infinity (open circuit).
- 📏 Between the starting winding and the housing: infinity (open circuit).
If the multimeter shows zero (short circuit) or infinity (open circuit) where there should be resistance, the compressor is faulty. Also a critical indicator is the resistance between any winding and the copper tube or housing - there should only be a break here.
In some cases, the resistance may be normal, but the engine hums and does not spin. This may indicate a mechanical wedge or pressure problem. However, the electrical part in this case is formally in good order.
Table of standard resistance indicators
For ease of comparison of the data obtained, we present a table with approximate values for various types of compressors. Remember that the exact data is always indicated in the manufacturer's technical documentation.
| Winding type | Normal resistance (Ohm) | Possible malfunction | Action |
|---|---|---|---|
| Starting | 20 – 50 | Open or short circuit | Replacement of compressor |
| Working | 10 – 30 | Interturn short circuit | Replacement compressor |
| Insulation (on the body) | Infinity (∞) | Breakdown on the body | Urgent replacement, dangerous! |
| Thermal protection | 0 (zero) | Open circuit | Replacing the thermal relay |
If your measurements differ radically from the table, further operation of the refrigerator is impossible without repair. Interturn short circuit often leads to knocked out plugs or automatic switches in the apartment.
Please note that the resistance may vary slightly depending on the engine temperature. A cold motor will have slightly less resistance than a warm one. This is a normal physical phenomenon associated with the heating of copper.
Checking for insulation breakdown and short circuit
One of the most dangerous malfunctions is an insulation breakdown when current begins to flow to the refrigerator body. This not only disables the equipment, but also creates a risk of electric shock for the user. You can check for breakdown using a multimeter or a special device - a megohmmeter.
To check, touch one probe of the multimeter (resistance measurement mode at maximum) to any winding contact, and the other to the stripped copper tube of the compressor or metal case. The device should show infinity (one in the most significant digit). Any other readings indicate a current leak.
If a breakdown is detected, using the refrigerator is strictly prohibited. Even if by some miracle it works, touching its metal parts will be deadly. In this case, replacement of the unit or professional rewinding is required, which is not economically feasible.
⚠️ Attention: In older models of refrigerators without grounding, an insulation breakdown could go unnoticed for a long time until someone gets an electric shock. Make sure that your outlet has a working ground circuit.
Sometimes breakdown occurs only when heated. Therefore, if the cold test shows nothing, but the machine knocks out after 15-20 minutes of operation, suspect thermal destruction of the insulation. At home, such a malfunction is difficult to identify.
Analysis of operation when turned on (test run)
If the electrical parameters are normal, you can try a short-term start. This is done only after a complete check of all circuits and provided that you are ready to immediately de-energize the device. Connect the refrigerator to the network and listen to the sounds emanating from the motor.
Normal operation is characterized by a quiet hum, which after 1-3 seconds is replaced by the smooth hum of a working compressor. If you hear a loud clicking, humming noise and silence (the motor is trying to start but cannot), the problem may be a stuck piston or low voltage.
There is a method of starting with a push-button extension cord, but it requires experience. If the engine hums for more than 10 seconds and does not start, turn it off immediately! Long-term operation in the “humming” mode burns out the windings in a matter of minutes.
If the launch is successful, monitor the heating of the housing. It should heat evenly and moderately. If one part is hot and the other is cold, or if heating occurs too quickly, there is a hidden malfunction.
Common mistakes during self-diagnosis
Beginners often make mistakes that lead to false conclusions. For example, measuring resistance without removing terminals may give an incorrect result due to parallel circuits. They also often forget to clean the contacts from oxides, which introduces an error in the measurements.
Another mistake is ignoring the condition of the wiring. A burnt-out compressor can be replaced, but in a week a new one will burn out, if the cause was a power surge or poor contact in the socket. Always check the entire power circuit.
Do not forget about the refrigerant. If the freon has completely leaked out, the compressor may run idle without cooling the chamber, but it will not immediately overheat. However, long-term operation without freon is harmful to the motor.
Is it possible to check the compressor without a multimeter?
Definitely not. You can only judge indirectly by sound and heating, but this will not give an understanding of the condition of the windings. Without the device, you will not be able to distinguish an open circuit from a short circuit.
What to do if the resistance of the windings is normal, but the refrigerator does not freeze?
Most likely, the problem is not in the electrics, but in the mechanics (the compressor is jammed) or in the circulation system (clogged, freon leakage). You need to call a technician with a pressure gauge manifold.
Why does a new compressor burn out immediately after installation?
The reasons may be poor-quality vacuumization of the system, moisture ingress, incorrect dosage of oil, or problems with the starting relay. Also, the culprit may be unstable voltage in the network.
How to determine which wire to connect where if there is no marking?
You need to ring the contacts. Between the working and starting windings the resistance will be greatest. The common wire will be the one where the sum of the resistances with the other two will give the resistance between them.
Is it dangerous to change the compressor yourself?
Yes, it is dangerous. In addition to electricity, there is pressurized gas and oil. Improper soldering may result in an explosion or fire. In addition, the system requires evacuation, which is impossible without a pump.