Has the refrigerator stopped freezing, but the compressor only makes a quiet hum or a characteristic click, after which it goes silent? In most cases, the culprit in this situation is start relay. This small but critical element is responsible for starting the compressor motor, providing the necessary impulse to the windings.
Understanding how it works start-protection devicewill help you not to panic and correctly diagnose the problem before calling a technician. Often, replacing this inexpensive part brings the refrigerator back to life in a matter of minutes, saving the budget on complex repairs.
In this article we will look in detail at what a start relay is, how it works, why it fails and whether it is possible to replace it yourself. You will learn how to distinguish a burnt part from other faults and what to look for when buying a new one.
The principle of operation of the starting relay
To understand the importance of this part, you need to briefly consider the operation of a single-phase asynchronous motor that is installed in your refrigerator. Such a motor has two windings: main (working) and starting. When connected to the network, the voltage is applied only to the main winding; the creating magnetic field is not enough to move the rotor.
Here it comes into play starting relay. At the moment of switching on, it closes the starting winding circuit, creating additional torque. As soon as the motor shaft begins to rotate and picks up speed, the relay opens the starting winding circuit, and the engine continues to operate on the main winding.
There are two main types of such devices, the principles of which differ significantly. Induction control relays (with a coil) close the circuit when voltage is applied, and open it under the influence of current when the engine enters operating mode. Thermal (PTC) relays operate based on changes in the resistance of the heating element.
⚠️ Warning: Attempting to start the compressor without a start relay or with shorted contacts may result in instantaneous burnout of the motor windings. Never ignore the absence of this element.
Modern models are most often equipped with PTC relay (posistors). They use a ceramic element, which heats up when current passes and sharply increases its resistance, actually breaking the starting winding circuit. This is a more reliable and simple design that does not have moving parts.
Types of starting relays: inductive and posistor
There are two main types of starting devices on the household appliances market, and they are not always interchangeable. Understanding the difference between them is necessary when selecting spare parts for repair.
Induction (electromagnetic) relays have a movable core and contacts. When current is applied, the core is drawn into the coil and closes the contacts of the starting winding. When the current drops (the engine starts), the core falls under the influence of gravity or a spring, opening the circuit. Such relays are often marked RTK, R-1, R-2 and are installed on old Soviet and some modern refrigerators.
Posistor (thermal) relays (labeled RTP, RTS) have no moving mechanical parts. Inside the case there is a posistor - a disk, which, when heated by current, changes the resistance from several Ohms to several kOhms. This property allows it to automatically turn off the starting winding 1-3 seconds after switching on.
It is important to know that posistor relays are often combined with thermal protection relay (bimetallic plate), which turns off the compressor when it overheats. In induction models, thermal protection is often a separate element hanging on the contacts.
Signs of a faulty starting relay
Diagnostics of a faulty starting relay usually does not require complex equipment. Symptoms of failure of this unit are quite specific and manifest themselves in the behavior of the compressor.
The most common symptom is that the refrigerator hums, but does not start. You hear a quiet hum or buzz for 3-5 seconds, then a loud click and then silence. After some time (from 30 seconds to several minutes), the cycle repeats. This triggers the thermal protection of the compressor, which turns off the power so that the engine does not burn out.
Another symptom may be a complete lack of response when turned on, although the light in the chamber is on. If the compressor is cold and does not make any sounds, the problem may be in the relay, thermostat or wiring.
- 🔊 Frequent clicks: Sounds every 10-20 seconds from the back of the refrigerator.
- 🔥 Compressor heating: The engine tries to start, hums and gets very hot, but is not cooling no.
- 🚫 Lights off: When trying to start, the circuit breaker in the electrical panel may trip (rarely, but it happens when there is a short circuit in the relay).
Sometimes the relay can “stick” in the closed state. In this case, the starting winding remains on constantly, which leads to rapid overheating and humming of the compressor. If you do not disconnect such a refrigerator from the network in time, you can damage the expensive unit.
Diagnostics and checking the part with a multimeter
Before buying a new spare part, you need to make sure that the problem is in the relay, and not in the compressor itself. To do this, you will need a multimeter (tester) and a minimum set of tools.
First you need to dismantle the relay. Unplug the refrigerator, remove the rear protective cover (if equipped) and the plastic casing from the compressor. The relay is usually placed on three contacts of the compressor and secured with a bracket or simply sits tightly in place. Carefully remove it, first remembering or photographing the position of the wires.
Visual inspection often gives the answer: if traces of burning, melted plastic, or the smell of burnt insulation are visible inside the case, the part definitely requires replacement. If there is no external damage, proceed to the “continuity test.”
Checking with a multimeter is performed in resistance measurement mode (Ohm). For posistor relays, the cold resistance between the contacts should be low (typically 10 to 60 ohms). If the device shows infinity (open) or zero (short circuit), the relay is faulty.
For induction relays, the integrity of the coil winding and the mobility of the core are checked. The coil resistance should also be within a reasonable range (tens of Ohms), and the core should move freely inside the coil without jamming.
Instructions for replacing the start relay
Replacing the start relay is one of the simplest operations in repairing refrigerators, accessible even to a beginner. The main thing is to follow safety precautions and the sequence of actions.
First, make sure that you purchased a relay with exactly the same markings as the part that was removed. Even if the connectors are visually similar, the electrical characteristics (response current, delay time) may differ, which will lead to incorrect operation of the compressor.
☑️ Checklist before replacing the relay
The replacement process is as follows:
- Remove the old relay by disconnecting the wires (if they are not on a common block) and removing it from the compressor contacts.
- Compare the new and old relay. Make sure that the location of the contacts and connectors matches.
- If the old relay had a separate thermal protection (a metal “tablet” with wires), carefully move it to the new relay or connect the wires to the corresponding contacts.
- Place the new relay on the compressor contacts. It should fit tightly and all the way.
- Connect the wires (if they were disconnected) according to the photograph taken earlier.
- Fix the relay with a metal bracket or strip, if provided for by the design.
⚠️ Attention: Do not use excessive force when placing the relay on the compressor contacts. The plastic may crack and the contacts inside the compressor may become damaged. Movements should be progressive and confident.
After installation, reassemble everything in reverse order, plug in the refrigerator and listen. If the compressor starts with a characteristic hum and after a few seconds switches to quiet, uniform operation, the repair was completed successfully.
Compatibility and markings table
When searching for a spare part, it is important to focus not only on the appearance, but also on the markings. Manufacturers use different codes, but the main types can be systematized.
| Relay type | Common markings | Application | Features |
|---|---|---|---|
| Induction | RTK-1, RTK-1-3, R-1, R-2 | Atlant, Minsk, old Indesit models | Has a movable core, position sensitive |
| Posistor (PTC) | RTP-1, RTP-2, RTS-11, 100M45 | Modern refrigerators, LG, Samsung | No moving parts, works in any position |
| Combined | RTK-X, RT | Freezers, powerful compressors | Combines start and thermal protection |
| Specific | Danfoss 101N0011, 101N0020 | Danfoss/Secop compressors | Requires precise selection of current (Ampere) |
Is it possible to use a relay from another refrigerator?
You can use a relay from another model only if the electrical parameters (rated current, starting current) and geometric dimensions of the contacts. Visual similarity does not guarantee performance. For example, a relay for a 1/4 HP compressor. will not fit a 1/3 hp motor
If you have not found an exact analogue by marking, you can select a relay based on the compressor power (indicated on the nameplate, for example, 1/5 HP, 1/4 HP) or by rated current. Universal relays often have adjustment or a wide range of compatibility.
Frequently asked questions and answers (FAQ)
How much does a starting relay cost and where to buy it?
The cost of a starting relay varies from 500 to 2000 rubles, depending on the type and manufacturer. You can buy it in spare parts stores for household appliances, at radio markets, or order online, knowing the marking of your compressor.
Is it possible to repair an old relay?
Repairing a starting relay is usually impractical. PTC resistors cannot be restored, and in induction relays it is difficult to restore the tightness and accurate calibration of the core. It is easier and more reliable to buy a new part.
Why does a new relay burn out immediately after installation?
If a new relay burns out, this may indicate problems with the compressor itself (turn-to-turn short circuit of the windings), a malfunction of the thermostat (the compressor works without interruptions) or power surges in the network. It is also possible that a relay with unsuitable characteristics was selected.
Does the position of the refrigerator affect the operation of the relay?
For induction relays with a moving core, the position matters - they only work in a certain position (usually with an upward arrow). Posistor (PTC) relays work in any position, since they have no moving mechanical parts.