How to choose the right start-up relay for a refrigerator

A sudden stop of the compressor or characteristic clicks that interrupt the hum of the motor often indicate a failure of the starting device. This is a compact but critically important unit, without which starting the engine is impossible. Start-protection relay takes on the role of a “starter” that supplies the primary impulse, and a “guard” that turns off the power during overloads.

Independent replacement of this part is a very real task for the home a master who can extend the life of the refrigerator for several more years. However, the market is full of modifications, and an error in selection will lead to repeated combustion of an expensive compressor. Accurate selection requires an understanding of the physical principles of operation and the ability to read labels.

In this article we will look at how different types of devices differ, how to decipher manufacturer codes and what parameters to pay attention to first. You will learn to distinguish original spare parts from universal analogues and understand when saving on the price of a part is unacceptable.

Principle of operation and types of starting devices

The main task of the device is to briefly apply voltage to the starting winding of the engine in order to create rotor torque. As soon as the shaft reaches the required speed, the starting winding must be turned off. If this does not happen, the engine will burn out. There are two main relay typetypes of relays used in household appliances.

The first type is induction (electromagnetic). Inside there is a coil connected in series to the working winding circuit. When starting, the current is high, the magnetic field draws in the core, which closes the contacts of the starting winding. When the speed increases, the current drops and the spring opens the contacts. Such models are often marked RT or RTP.

The second type is posistor (PTC). Here, instead of mechanical contacts and a coil, a thermistor (posistor) is used. When cold, it has low resistance and allows current to pass through. When heated, its resistance increases sharply, actually breaking the circuit. These are more modern and reliable elements, often labeled as PTC or CSR.

⚠️ Attention: Induction and posistor relays are not always interchangeable. Replacing one type with another is possible only if this is directly stated in the technical documentation for a specific compressor or if you are changing the “relay + capacitor” pair.

Key parameters for selecting an analogue

To find a suitable replacement, it is not enough to just know the brand of the refrigerator. The compressors inside may be different. The main reference point is engine power, expressed in horsepower (HP) or watts. It is this parameter that determines the current strength that the device must withstand.

The second critical parameter is diameter of the mounting hole under the compressor rod. Standard values ​​vary from 12 to 14 mm, but there are also non-standard options. If the relay is not seated tightly, vibration will lead to broken contacts or overheating.

It is also necessary to take into account the type of refrigerant the compressor is designed to work with (R134a, R600a, R12). Although the relay itself may be mechanically suitable, the electrical characteristics of the contacts may vary in different environments. Universal models often have a wide range of compatibility.

Deciphering the markings of popular brands

Manufacturers use different coding systems, which often confuses when searching for a replacement. Understanding the logic of brands allows you to quickly find analogues. For example, the company Indesit often has relays with codes starting with 123456, where the last digits may indicate a modification.

Brand Atlant (Atlant) uses markings that often include the word “Start-proof” and a numeric code, for example, P-3. Refrigerators Beko and LG are characterized by compact black posistors, where the power is indicated directly on the case (for example, 1/4 HP, 1/5 HP).

The table below shows common marking correspondences for popular compressors:

When searching in online stores, use cross codes. Often the same physical element is sold under different article numbers for different brands of refrigerators. The matching of current (Ampere) and power (HP) is more important than the matching of the logo on the case.

Instructions for dismantling and installation

The replacement process does not require complex tools, but requires compliance with safety precautions. Before starting work, be sure to disconnect the refrigerator from the power supply. Access to the relay is usually located at the lower rear of the unit where the compressor is located.

Remove the protective cover (if equipped) and disconnect the wire connectors. The old device fits tightly onto the three contact pins of the compressor. It must be carefully loosened and removed. Be careful, the contacts may oxidize.

Installation of the new element is carried out in the reverse order. It is important to orient the part correctly: on the body there is usually an arrow UP or an inscription TOPthat should look straight up. Incorrect orientation will disrupt the operation of the mechanics or heat dissipation.

⚠️ Attention: If, when removing the old relay, you find black carbon deposits, melted plastic inside, or smell a burning smell, this is a normal sign of failure. However, if the contacts on the compressor itself are also blackened, they must be cleaned with fine sandpaper before installing a new part.

Universal kits: is it worth buying?

So-called “universal starting relays” are often found on the market (for example, 41K148, 6WR, 88R). They are positioned as a solution for a wide range of compressors from 1/8 to 1/2 HP. The kit often includes a capacitor and a set of adapters.

The advantage of such solutions is availability and low price. They can actually start the engine if the original cannot be found. However, their service life is usually lower than that of standard induction relays. The contact closure mechanism in them is less accurate.

Why do universal relays heat up more?

Universal posistors often have a less efficient heat sink and are designed for average operating conditions. Unlike factory relays selected for a specific winding inductance, they can operate with slight overheating, which shortens their service life.

It is recommended to use universal kits as a temporary solution or for discontinued refrigerators, where the originals are unreasonably expensive. For modern equipment with inverter compressors, such relays are absolutely not suitable.

Fault diagnosis and common errors

How to understand that the problem is in the relay? If the refrigerator hums for 3-5 seconds, then a click is heard and the humming stops (and so on in a cycle) - this is a classic symptom. The compressor tries to start, the relay is triggered, but the engine does not pick up speed, and the protection turns off the power.

A common mistake made by amateur repairmen is replacing the relay without checking the compressor itself. If the motor is jammed or there is an interturn short circuit in the windings, the new relay will burn out in a few minutes. Before purchasing a part, it is advisable to “ring” the windings with a multimeter.

• 🔌 Checking the contacts: Shake the relay near your ear. If you hear a ringing sound (like a coin), it means that the contacts inside are loose or broken off - the part is faulty.
• 🔥 Visual inspection: A melted case or blackened wires indicate an overload, possibly due to poor contact or low voltage in the network.
• 🧊 Capacitor: When replacing an induction relay, always replace the starting capacitor. The old one may have a changed capacitance, which will lead to difficult starting.

When professional help is required

Despite the apparent simplicity, there are situations when independent repair is dangerous. If after replacing the relay the refrigerator does not start, but the new element instantly heats up or knocks out the circuit breakers in the panel, the problem is deeper. There may be a short circuit in the wiring or a breakdown in the housing.

It is also worth contacting a specialist if soldering of the copper circuit or vacuuming of the system is required. Working with refrigerant requires a license and special equipment. Do not try to open the sealed compressor casing yourself.

Is it possible to install a relay of greater power than was installed?

Technically, a more powerful relay can start the compressor, but this is dangerous. The contacts will close at a current for which they are not designed, which will lead to their rapid burning. In addition, the thermal protection may not work, and the compressor will burn out when jammed.

Why does the new relay burn out after a week?

There may be several reasons: incorrectly selected power (too weak), poor contact at the compressor terminals (sparking), malfunction of the compressor itself (difficult start) or low voltage in the network, because of which the relay does not have time to turn off the starting winding.

What is the difference between the relay for R134a and R600a?

The main difference is in the refrigerant and oil, as well as in the design of the compressor. Relays for R600a (isobutane) often have more stringent intrinsic safety requirements since isobutane is explosive. It is not recommended to use a relay from R12/R134a to R600a without consulting the manufacturer.