A sudden stop of the refrigerator often confuses the owner, especially if the unit hums but does not start, or makes clicking noises. In most cases, the cause of the breakdown is the failure of the start relay - a small but critical component in the compressor engine starting system. It is this element that supplies the necessary impulse to the starting winding, allowing the motor to gain speed and begin pumping refrigerant.
Replacing this part yourself is a real task for a home craftsman, which can save a significant amount on calling a specialist. However, the success of the operation directly depends on how accurately you select an analogue to replace the burned-out device. The wrong choice can lead to repeated breakdown or even failure of the compressor itself, so the issue of marking and compatibility must be approached with the utmost care.
Principle of operation and types of starting devices
The starting relay is an electromechanical switch that closes the circuit of the starting winding of the electric motor only at the moment of starting. As soon as the compressor rotor reaches the required rotation speed, the relay opens the contacts, turning off the starting winding, and the engine continues to operate on the main winding. There are two main types of such devices: induction (electromagnetic) and posistor (thermal).
Induction relays work due to the electromagnetic force of current flowing through a series winding. When the starting current is high, the core retracts and closes the contacts. After the engine accelerates, the current drops and the spring returns the core, opening the circuit. Such models are often found in old Soviet refrigerators and have a characteristic vertical installation at the compressor terminals.
Posistor relays use a thermoelement (posistor), which, when heated by current, sharply increases its resistance, actually breaking the circuit. They are more compact, often combined with a thermal protective relay and are less sensitive to vibrations. Modern models of refrigerators, such as Indesit, Stinol or Atlant, are most often equipped with posistor options.
⚠️ Attention: Visually, inductive and posistor relays may look similar, but they are not interchangeable. Installing the wrong type of device is guaranteed to lead to burnout of the compressor windings or constant operation of the engine with overheating.
Differences in design also dictate the method of their installation. Induction models often require a strict vertical orientation ("arrow up"), as they operate under the influence of gravity. PTC devices are more versatile, but they also have limitations on the angle of inclination. Understanding the type of relay you have is the first step to a successful repair.
Diagnosing the problem before replacing
Before you go to the store for spare parts, you need to make sure that the problem lies in the start relay, and not in the compressor or wiring. Symptoms may be similar, so careful checking is important. If the refrigerator turns on, there is a click, a hum lasts a few seconds, followed by another click and silence - this is a classic sign of a faulty starter or a jammed motor.
For an accurate diagnosis, remove the relay from the compressor housing (after disconnecting the refrigerator from the mains!). Visually inspect the housing: the presence of soot, cracks or melted plastic indicates overheating. If there is no external damage, you can try to “shake” the device near your ear: if you hear the ringing of a broken ceramic element or a dangling core inside, the part definitely requires replacement.
- 🔍 Check with a multimeter: Ring the relay contacts in a cold state - the resistance should be minimal, and when heated (for a posistor) it should go to infinity.
- 🔌 Audit of contacts: Oxidized or burnt contacts on the terminals can prevent normal starting, even if the relay itself is working properly.
- 🌡️ Thermal sensor test: If the relay is combined with thermal protection, check the continuity of the protection circuit; it should not be broken at room temperature.
Sometimes the cause of failure is not the relay itself, but insufficient voltage in the network or a malfunction of the thermostat. However, if the compressor hums, then there is voltage and the thermostat has closed the circuit. In this case, the probability of failure of the starting device is more than 80%. Do not rush to throw away the old part immediately after removal - the marking on it will be your main guide.
Marking and decoding manufacturer codes
Selecting an analogue is the most critical stage. Refrigerator manufacturers rarely make relays themselves, purchasing them from specialized companies like Danfoss (Secop), Indesit, Start or PTC. The body of the part is always marked with a code, which consists of letters and numbers. For example, popular relays RT or RS have clear numbering, where each number corresponds to a certain compressor power.
Often, the same refrigerator can have relays from different brands of component manufacturers. For example, in refrigerators Atlant you can find both native Belarusian relays and Chinese analogues or Italian Italtecnica. The main thing here is the correspondence of the electrical characteristics: voltage (usually 220V), operating current and, most importantly, the diameter of the mounting holes for the compressor pins.
Pay attention to the location of the contacts. There are models with three terminals (common, starting, working) and with four, where a contact for a fan or additional protection is added. The shape of the case is also important: rectangular, round or teardrop-shaped. If you cannot find an exact analogue by article number, you can select a replacement based on the compressor power indicated on the engine nameplate (for example, 1/5 HP, 1/4 HP).
Power correspondence table
A compressor power of 1/5 HP corresponds to a current of approximately 1.0-1.3 Amperes. 1/4 HP requires a 1.4-1.7 Ampere relay. Exceeding the relay current will lead to its rapid combustion, and underestimating it will make it impossible to start the motor.
In some cases, the markings may be erased or unreadable. Then you have to focus on the number of contacts and their geometry. Take a photo of the old part from all sides before going to the store - this will help the consultant quickly find the right spare part in the catalog.
Compatibility table and popular models
To simplify the search, we provide data on the most common types of relays used in household appliances. This table will help you navigate the variety of articles, but remember that manufacturers can change component suppliers in different batches of equipment.
| Relay type | Article / Marking | Compatible brands | Current (Ampere) |
|---|---|---|---|
| Posistor | RTS11105 (116005) | Indesit, Ariston, Stinol | 1.0 - 1.3 |
| Posistor | RS-11N (117001) | Atlant, Biryusa, Nord | 1.1 - 1.4 |
| Induction | R-6 (R-6) | Soviet refrigerators | 1.3 - 1.6 |
| Universal | PTC Relay (set) | Suitable for many 1/4-1/3 HP | Adjustable |
Universal kits, often called "3 in 1", include a relay, thermal protector and capacitor. They are positioned as a replacement for a wide range of compressors. The use of universal kits is permissible only in emergency cases when the original cannot be found, since their service life and operating accuracy are often inferior to standard parts.
When choosing, pay attention to the diameter of the holes for the compressor pins. Standard dimensions may differ by fractions of a millimeter, which will lead to loose contact or the inability to tighten the relay onto the terminals. A tight fit without play is critical for reliable current transfer and heat dissipation.
Step-by-step instructions for replacing the relay
The process of replacing the start relay does not require complex tools, but does require compliance with safety precautions. Before starting work, be sure to disconnect the refrigerator from the electrical network. Unplug the cord from the outlet - this is the first and most important rule, ignoring which can lead to electric shock.
Remove the rear protective panel (casing) at the bottom of the refrigerator where the compressor is located. It is usually secured with latches or several bolts. Once you reach the compressor, you will see a box at the end of the engine, secured with a clamp or clip. Carefully remove the fixing bracket and pull the box off the compressor terminals.
☑️ Algorithm for replacing the relay
Remove the old relay from the housing. Now look carefully at how the wires fit into it. Usually there are two or three. Disconnect the terminals, noting (or marking) their locations. Install the new relay into the housing in the correct orientation (the "UP" marking or arrow should face up). Slide the wire terminals onto the corresponding pins of the new device.
⚠️ Attention: Do not use excessive force when placing the relay on the compressor pins. The fragile plastic of the case can crack, and the pins themselves can bend, which will make the compressor unrepairable at home.
Assemble the structure in reverse order: insert the relay with wires into the casing, put the casing on the compressor until a characteristic click is heard and secure with a bracket. Reinstall the protective panel. Plug in the refrigerator and listen: if after a few seconds you hear the smooth hum of a running motor and after 10-15 minutes cold appears, the repair was successful.
Frequent errors during selection and installation
One of the most common mistakes is ignoring thermal protection. In many modern models, the relay and thermal relay (overheat protection) are a single unit or tightly connected. Trying to save money, craftsmen change only the starting part, leaving the old, “tired” protection. This leads to the new element burning out after a couple of days due to untimely shutdown during overload.
Another mistake is installing a higher power relay “just in case.” The logic “the more powerful the better” does not work here. If the cutoff current is too high, the relay will not open the starting winding in time. It will burn out and the compressor will fail. Exact matching of the amperage is the key to the longevity of the repair.
They also often forget to check the capacitor if it is in the circuit. In old induction relays, a capacitor can be installed in parallel, which improves the starting torque. If it is swollen or has lost capacity, even a working relay will not be able to start the engine under load. Always check the entire chain of the starting unit.
Do not forget that the compressor is the heart of the refrigerator, and the starting relay is its valve. Take the selection of this part seriously, check the markings and do not be afraid to double-check compatibility in catalogs. A high-quality spare part and careful installation will return years of service to your refrigerator.
Can a universal relay be used for any refrigerator?
Universal relays (3-in-1 kits) are suitable for most compressors with a capacity of 1/8 to 1/2 horsepower, but they do not always perfectly match in geometry fastenings. In addition, their temperature characteristics are averaged, which can shorten the service life of the compressor compared to the original relay.
Why did the new relay burn out immediately after installation?
This may indicate a more serious problem: an interturn short circuit in the compressor windings, a jammed piston group, or a malfunction in the electrical network (voltage surges). Also, the cause could be poor contact in the connectors, which caused sparking and overheating.
Where to find the markings if they are erased on the housing?
If the markings are unreadable, focus on the compressor model (indicated on the sticker on the motor housing). Based on the compressor model on the Internet, it is easy to find the specification and the required type of starting relay. You can also measure the diameter of the pins and the distance between them with a caliper.
What is the danger of using a relay with a lower cut-off current?
A relay with a lower current can open the circuit too early, preventing the engine from gaining the required speed. This will lead to the fact that the compressor will constantly try to start, click and hum, but will not reach operating mode, which will quickly disable it.