Sudden stoppage of the refrigerator or a characteristic click, followed by the hum of the motor, but without starting, often indicate a way out the starting device is faulty. This is a small part that plays a critical role in the electrical circuit to ensure that the compressor motor starts. Without a working relay, the motor will not be able to overcome the initial inertial resistance and enter the operating mode.
The correct one selection of a relay for a compressor is not just buying the first part that comes along with a similar appearance. An error in selection can lead to re-burning of the spare part, damage to the motor windings, or even fire of the wiring. In this article, we will analyze in detail the principles of operation of the device, diagnostic methods and the exact criteria for choosing a replacement for various models of equipment.
Before going to the store or looking for a part on the Internet, you need to understand what exactly has failed. Users often confuse the starting relay with a thermal protector, although they perform different functions. Thermal relay protects the motor from overheating by opening the circuit at critical temperatures, while the starting relay is responsible for short-term voltage supply to the starting winding.
Principle of operation and types of starting ones devices
The main task of the starting relay is to briefly connect the starting winding of the motor stator when the refrigerator is turned on. As soon as the rotor reaches the required speed, the device must turn off this winding, leaving only the main one working. There are two main types of such devices, which differ fundamentally in design and selection method.
The first type is induction (electromagnetic) relays. They are based on a coil through which the current of the main winding passes. When starting, the current is high, the magnetic field draws in the core, which closes the contacts of the starting winding. When the motor accelerates, the current drops and the core, under the influence of gravity or a spring, lowers, opening the circuit. Such models are often marked with the letters RT, RTK, P-3.
The second type is posistor (thermal) relays. An element with a positive temperature coefficient of resistance (posistor) is used here. When cold, it has low resistance and passes current to the starting winding. When current passes, the posistor heats up, its resistance increases sharply, and the current practically stops. Such devices are designated by the marking P-1, P-2, PTC.
- 🔌 Induction relays operate on the basis of an electromagnetic field and are sensitive to orientation in space (often have an "UP" arrow).
- 🔥 Posistor relays use heating the crystal to break the circuit and are less sensitive to position, but are afraid of moisture.
- ⚙️ Combined devices can contain both a starting and a thermal protector in one housing, which complicates their replacement.
Diagnostics: how to understand that the relay faulty
Before looking for a replacement, you need to make sure that the problem lies in the starting device, and not in the compressor itself. The symptoms of a malfunction are usually quite clear: the refrigerator hums for 3-5 seconds, then a click is heard and the motor stops. After some time, the cycle repeats. This indicates that the starting winding is not disconnected or not connected at all.
For accurate diagnostics, the relay must be removed from the compressor. It is located in a black casing at the back of the unit, mounted on three motor pins. After removing the protective cover and disconnecting the wires, inspect the device visually. There should be no cracks, melting or traces of burning on the body. If a ringing sound is heard inside when shaken (for induction), this is a sign of destruction of the core or contacts.
⚠️ Attention: Before removing the relay, be sure to disconnect the refrigerator from the power supply! Touching live parts under voltage is deadly.
The functionality can be checked using a multimeter. For a posistor relay in a cold state, the resistance between the contacts should be low (tens of ohms). If the multimeter shows infinity or, conversely, zero (short circuit), the part requires replacement. The induction relay is checked for an open circuit in the coil and mobility of the core.
It is also important to check the condition of the contacts on the compressor itself. If the studs are oxidized or burnt, the new relay can quickly fail. Clean the contacts with fine sandpaper before installing the new part. Do not use aggressive chemical solvents for cleaning, which can damage the insulation.
Selection criteria: power, current and brand
The most reliable way to select an analogue is to look for the part by the markings stamped on the body of the old relay. However, if the original part cannot be found, interchangeable analogues can be used. The key parameters here are motor power and starting current. Incorrect selection of these parameters will result in the relay either not starting the motor or not turning off the starting winding.
The compressor power is usually indicated on the nameplate of the engine itself (for example, 1/5 HP, 1/4 HP) or in the technical documentation of the refrigerator. The power can also be determined by the current consumption indicated on the refrigerator tag. Some models are suitable for low-power motors up to 150 W, while completely different ones are suitable for powerful inverter or dual-motor systems.
When looking for an analogue, pay attention to the country of origin and series. European, Chinese and Russian relays may have different housing geometries, but the same electrical characteristics. The main thing is that the distances between the contacts coincide with the landing pins of your compressor.
- 📏 Contact geometry: the distance between the pins must match exactly, otherwise the relay will not fit or will dangle.
- ⚡ Starting current: must correspond to the engine power (usually from 100 to 400 W).
- 🏷️ Orientation: induction relays often require installation strictly vertically (marked "UP" or up arrow).
Below is a table of correspondence between popular relay models and their analogues, which will help you navigate when purchase:
| Original marking | Type | Power (W) | Possible analogue |
|---|---|---|---|
| RTK-1, RTK-1-3 | Induction | up to 130 | R-3, 33.00605.000 |
| R-1, R-2 | Posistor | up 150 | PTC 15M1, 117610 |
| RTK-X-3 | Induction | up to 220 | R-4, 130112 |
| Danfoss 101N0213 | Posistor | up to 250 | PTC 7-9, 120147 |
Is it possible to use a relay of higher power?
Theoretically, a relay designed for higher power can start the motor, but there is a risk that it will not turn off the starting winding in time, since the current in the circuit will be “too small” for it. This will lead to overheating and burning of the motor winding. It is better to use an exact analogue or a device with slightly less, but not more power.
Step-by-step instructions for replacing the relay
Replacing the start relay is a procedure that is accessible even to a beginner, if you are careful and follow the sequence of actions. The main thing here is not to damage the compressor tubes and connect the wires correctly. Before starting work, make sure that you have purchased a part with the identical number of contacts and their arrangement.
First, remove the back cover of the refrigerator (if there is one) and get to the compressor. Carefully remove the plastic casing covering the electrical part of the motor. You will see that the relay is put on three pins. Remember or take a photo of which wire goes where, although usually the colors of the wires correspond to the standard diagram.
☑️ Checklist before replacement
Remove the old relay by pulling it down or shaking it from side to side. If it is stuck, do not use force - it is better to carefully trim the plastic so as not to break the compressor studs. Disconnect the wires from the old device. Connect the wires to the new relay, observing the color coding. Usually the phase wire goes to one contact, and the zero to the other, but it is better to use the diagram on the case as a guide.
Install the new relay on the compressor studs. It should fit tightly and not wobble. For induction models, it is critical to maintain a vertical position: the arrow UP must look up. If installed upside down, gravity will not be able to lower the core and the starting winding will not turn off.
⚠️ Warning: Do not attempt to start the compressor without the protective housing and cover. This breaks the insulation and can lead to electric shock if accidentally touched.
After installation, reassemble everything in reverse order. Plug in the refrigerator. It is considered normal to start the engine 1-2 minutes after turning it on. If the motor hums but does not start, or the machine immediately knocks out, immediately turn off the power. This means that the wrong relay has been selected or the problem is deeper (jammed compressor, breakdown of the windings).
Frequent errors during selection and installation
One of the most common mistakes is ignoring the type of compressor. The relays described above are suitable for standard asynchronous motors. However, modern refrigerators are often equipped with inverter compressors. In such systems, there is no starting relay as a separate element - the engine is started and controlled by an electronic control unit. Trying to find and replace the “relay” on an inverter motor is a pointless waste of time.
Another mistake is using low-quality universal Chinese relays. They may have stated characteristics, but in reality their calibration is broken. Such a relay may turn off the starting winding too early (the motor will not start) or too late (the winding will burn out). It’s better to overpay for the original or a proven brand like Danfoss, Secop or Atlant.
Also, users often forget about the thermal protector. If the start relay burns out, there is a high probability that the thermal protection was overloaded. If you change the starter but don't check the thermal fuse, the new unit can quickly fail due to lack of overheating protection. In combined devices, the entire unit is changed.
- 🚫 Ignoring inverters: inverter compressors do not have a classic starting relay.
- 💸 Saving on quality: cheap analogues often have a spread of parameters up to 30%.
- 🔧 Orientation violation: installing the induction relay horizontally or with the arrow down.
FAQ: Frequently Asked Questions
Is it possible to start a refrigerator without a relay?
Theoretically, you can start an asynchronous motor by manually applying voltage to the starting winding, but this is extremely dangerous and requires the skills of an electrician. In domestic conditions, it is impossible to operate a refrigerator without a relay: the motor will not be able to reach operating mode on its own, it will hum and quickly burn out due to overheating of the windings.
Why does the new relay immediately burn out?
If the new relay burns out after a few seconds or minutes of operation, there may be several reasons: a part with an inappropriate cutoff current was selected, it is jammed compressor (the motor consumes starting current constantly), or an insulation breakdown of the motor windings has occurred. A short circuit in the refrigerator wiring is also possible.
Where can I find the relay markings if they are erased?
If the markings on the case are not readable, you will have to select an analogue based on the compressor power. Look at the engine nameplate (the black barrel on the back): it shows the power in watts (W) or horsepower (HP). You can also find the model of the refrigerator and look at the specification for the type of installed compressor.
How much does it cost to replace a relay in the service?
The cost consists of the price of the part itself (from 300 to 1500 rubles depending on the model) and the cost of the technician’s work. In service centers, the price for departure and replacement can vary from 1,500 to 3,000 rubles. Self-replacement saves the budget, but requires tools and minimal skills.