Refrigerators Atlant are deservedly popular due to their reliability and affordability, but even the highest quality equipment breaks down over time. One of the most common reasons why a unit stops cooling or starts to work intermittently is a malfunction of the compressor start-up mechanism. It is thermal relay responsible for the safe start of the engine and its protection from overloads, so diagnosing it is the first step when searching for a breakdown.
If you notice that the engine is humming, but does not start, or, conversely, it turns on immediately clicks off, the problem most likely lies in the start control circuit. Self-checking this unit allows you to save a significant amount on calling a technician and quickly return the refrigerator to operation if the part really requires replacement.
In this article we will analyze in detail the design of the protective unit, consider diagnostic methods using a multimeter and without instruments, and also answer frequently asked questions from equipment owners. Atlant. Understanding the operating principle of this small but important part will help you avoid mistakes during repairs and correctly assess the condition of the compressor.
The operating principle and design of the start-up protection relay
The start-up protection relay, which is often called simply thermal, is a combined device that combines the functions of starting an asynchronous motor and protecting it windings from overheating. In the design of refrigerators Atlant most often there are relays of the RT, RZ series or more modern solid-state analogues, but the principle of their operation is based on the physical properties of a bimetallic plate.
When the refrigerator is turned on, current passes through the heating element of the thermal relay, causing it to heat up. The bimetallic plate bends under the influence of temperature and closes the contacts of the starting winding, allowing the compressor rotor to gain the required speed. As soon as the engine starts, the current drops, the plate cools down and opens the starting winding circuit, leaving only the main winding to work.
Key element here is the sensitivity of the plate to current and temperature. If the compressor tries to start but is stuck or the line voltage is too low, the current remains high. The plate gets hotter than usual and opens the contacts, cutting off power to the motor to prevent it from burning out. This mechanism is critical for the durability of the motor.
⚠️ Attention: The thermal relay is selected strictly for a specific compressor model. Installing a part with inappropriate cut-off current parameters can lead to false alarms or, conversely, burnout of the motor windings.
It is worth noting that in older models Atlant there may be relays with an open design, where the spiral and plate are visible, while in new ones they are enclosed in a black plastic case. Despite the external differences, working algorithm they are identical, which simplifies the diagnostic process for the home master.
External signs of a faulty protective mechanism
Before disassembling the refrigerator and Before you get the tools, you need to carefully analyze the symptoms that the unit exhibits. Often, the nature of the sounds and the frequency of operation of the compressor can accurately indicate that the problem lies in the relay, and not in the motor itself or the refrigerant circulation system.
One of the most obvious signs is a characteristic click that is heard a few seconds after turning on the motor, followed by silence. The compressor may hum as it tries to start, but the relay breaks the circuit and the process repeats cyclically. This indicates that the protection is triggered due to the impossibility of the engine reaching operating mode.
It is also worth paying attention to the temperature of the relay housing. If, after attempting to start, the plastic or metal body of the device becomes hot or even charred, this is a sure sign overcurrent or an internal short circuit in the relay itself. A visual inspection can also reveal cracks in the body or melted contacts.
Sometimes the malfunction manifests itself in the fact that the refrigerator runs continuously without turning off. In this case, the relay could “stick” in the closed state, constantly supplying voltage to the starting winding, which is extremely dangerous for the engine. In such a situation, it is necessary to immediately disconnect the device from the network to avoid a fire.
Removing the relay for diagnostics
To conduct a quality check, the device must be removed from the refrigerator. This procedure does not require complex tools, but requires compliance with safety precautions and care so as not to damage fragile wiring elements.
First of all, the refrigerator must be completely disconnected from the electrical network. Unplug the cord from the outlet and provide access to the compressor, which is usually located in a niche on the back wall of the unit. Let the motor cool for 15-20 minutes if it was running before.
On the compressor you will see a box placed on the motor rod. It can be attached simply due to the tightness of the fit or additionally fixed with a spring clip. Carefully remove the casing by bending the fasteners or unscrewing the screws, if present.
- 🔌 Disconnect the power connector coming from the refrigerator wiring to the relay by pulling the chip body, not the wires.
- 🛠️ Remove the starting and thermal relay from the compressor pins, rocking them from side to side without excessive effort.
- 🧹 Clean the surface from dust and cobwebs so that they do not get inside the motor during further operation.
After removal, inspect the device for external damage. If traces of burning are visible on the body, and parts are loose inside, further inspection may not be required - the element definitely requires replacement. However, to be completely sure, it is better to carry out instrumental diagnostics.
Checking the relay with a multimeter: step-by-step instructions
The most accurate diagnostic method is to check the electrical characteristics using a multimeter. This device will allow you to determine the integrity of the internal circuits and the compliance of the resistance with the standard, which cannot be done “by eye.”
Switch the multimeter to the resistance measurement mode (Ohm) to a limit of 200 Ohms. First, check the circuit of the thermal element itself. The probes of the device must be applied to the input and output contacts of the thermal relay. In a cold state, the contacts should be closed, and the device should show a resistance close to zero.
Next, the coil or contacts responsible for the starting winding are checked. Here the resistance should also be minimal. If the device shows one or infinity, this indicates open circuit, and the relay will not be able to perform its startup function.
☑️ Diagnostics with a multimeter
Pay special attention to the condition of the contacts. If the resistance in the closed state is high or floating, this indicates carbon deposits or oxidation inside the device. In such cases, the relay may operate unstably, causing periodic failures of the refrigerator.
⚠️ Attention: Never measure resistance while the device is connected to the network or has not cooled down after operation. This may damage the multimeter and cause electric shock.
There is also a heat test method, but it requires caution. You can apply low voltage to the relay heating element and see that after a certain time the contacts open with a characteristic click. However, at home, it is safer to rely on checking the continuity of the circuit in a cold state.
Table of typical faults and methods for eliminating them
For the convenience of systematizing possible problems when checking the thermal relay of refrigerators Atlant, we have compiled a summary table. It will help you quickly compare the obtained measurement results with the probable cause of the malfunction.
The table shows the main conditions that you can detect during the diagnostic process. Remember that a combination of several symptoms may indicate more complex problems affecting not only the relay, but also the compressor itself.
| Symptom when checking | Probable cause | Action |
|---|---|---|
| Infinite resistance | Broken bimetallic plate or coil | Replacing the relay with a new one |
| Resistance is normal, but does not click | Mechanical jamming or loss of elasticity | Replacement relay |
| Contacts do not open when heated | Welding of contacts or plate defect | Urgent replacement to avoid fire |
| Resistance too high | Oxidation of contacts or bad contact | Wipe (temporarily) or replace |
Using this data, you can accurately determine whether your current unit can be restored or needs to be disposed of. In most cases, repairing the relay itself is impractical, since a new part is inexpensive, and the reliability of the restored device will be in question.
Is it possible to temporarily close the relay?
Theoretically, if you close the contacts of the thermal relay, the compressor will start directly. However, this is extremely dangerous: with any overload, the engine will not receive protection and will burn out in a few minutes. Use this method only for short-term testing of the compressor under constant current monitoring.!
Nuances of selecting and replacing parts for Atlant
If the test shows that the thermal relay is faulty, you are faced with the task of finding a suitable replacement. The market for spare parts for refrigerators Atlant is wide, but it is important to choose an analogue with identical electrical characteristics.
First of all, pay attention to the markings of the old device. The numbers and letters printed on the housing contain information about the cut-off current and the type of compressor for which the relay is intended. For example, marking RT-K indicates certain parameters that must match for a new part.
Also consider the type of compressor: piston and linear motors may require different types of starting devices. An error in selection may result in the refrigerator either not starting or constantly knocking out the protection.
The process of installing a new relay is simple: it is put on the pins of the compressor until it stops and is fixed. The main thing is to make sure that the contacts fit tightly, and the device itself sits evenly, without distortion. After installation, assemble the casing and turn on the refrigerator.
Frequently asked questions (FAQ)
At the end of the article, we will answer several questions that most often arise among refrigerator owners Atlant when doing their own repairs.
Is it possible to test a relay without a multimeter?
Yes, there is a “shaking” method. If you hear a knocking sound from the internal part when you shake the relay near your ear, this may mean that the bimetallic strip has come off or has become deformed. You can also carefully apply power directly to the compressor (bypassing the relay) for a split second: if the motor starts, then the problem is in the relay. However, this method requires the skills of an electrician.
Why does a new relay burn out immediately after installation?
If a new relay fails quickly, the reason is most likely not in it, but in the compressor itself. An interturn short circuit in the motor windings creates an increased current, which “burns out” the protection. Also, the cause may be unstable voltage in the network or a faulty wiring of the refrigerator.
How often do you need to change a thermal relay?
A thermal relay is a part that does not have a specific service life and is replaced only after a breakdown. Under normal operating conditions and stable mains voltage, it can serve for decades together with the compressor.
What is the difference between a starting and thermal relay?
They are often combined into one housing. The starting one is responsible for short-term supply of voltage to the starting winding for starting, and the thermal one is responsible for breaking the circuit during overload. In modern devices Atlant these functions are often combined in one unit.
Is it dangerous to operate a refrigerator with a faulty relay?
Yes, it is dangerous. If the relay does not open the circuit when overloaded, the compressor may overheat, causing insulation melting, short circuiting, and even fire. In addition, constant attempts to start without protection quickly damage the engine itself.