Humming or characteristic clicks of the compressor in the absence of cold in the refrigerator chambers almost always indicate a burnt-out starting relay - the key element that supplies the starting impulse to the motor windings. It is the failure of this compact unit, caused by sticking contacts or thermal breakdown, that prevents the motor from gaining operating speed and leads to a break in the electrical circuit, requiring immediate replacement of the part to restore normal operation of the unit.
Owners often wonder: is it possible to find a replacement for a burnt-out component if the original part is discontinued or cannot be found in local stores? Fortunately, the spare parts market offers many universal solutions and analogues. However, simply buying the first “box” you come across can lead to repeated breakdown or even burning of the motor windings. You need to know exactly the parameters, type of connection and compatibility with your compressor.
In this article we will look at how to determine the type of faulty relay, what can replace it, how to read the markings and what to look for when installing an analogue. You will learn about the differences between inductive and posistor devices, understand why you can’t just connect the wires directly, and get a step-by-step algorithm for doing your own repairs. A correctly selected analog will extend the life of your refrigerator for many more years.
Diagnostics and signs of a faulty starting relay
Before looking for a replacement, you need to make sure that the problem lies in the starting device, and not in the compressor or thermostat itself. The first sign of a malfunction is a characteristic sound: a series of clicks at intervals of several seconds or minutes. The compressor tries to start, hums, but after a moment there is a click and the motor stops. This triggers the thermal protection relay, since the current in the circuit exceeds the norm due to the fact that the rotor does not rotate.
Visual inspection often helps to make an accurate diagnosis without complex instruments. If you remove the relay cover, you may find traces of soot, melted plastic, or blackened contacts. Sometimes the device case has cracks due to overheating. In the case of posistor models (PTC), there may be no external signs, so a check with a multimeter is required. The resistance of a working posistor at room temperature should be 20–60 Ohms, and when heated it should go to infinity.
It is also worth paying attention to the condition of the capacitor, if there is one in the circuit. Swelling or electrolyte leakage indicates that starting capacitor also requires replacement. Often these elements are replaced in pairs, since a malfunction of one could provoke an overload of the other. Ignoring the diagnostics of the capacitor when replacing the relay can lead to rapid failure of the new part.
⚠️ Attention: If, after replacing the relay, the compressor continues to hum and knock out the protection, the problem may lie in the turn-to-turn short circuit of the motor windings or the wedge of the piston group. In this case, further attempts to start may finally finish off the motor.
Types of starting relays and the principle of their operation
Understanding how your device works is critical for selecting an analogue. There are two main types of start relays used in household refrigerators: induction (electromagnetic) and posistor (thermal). Induction relays operate on the basis of an electromagnetic coil, which, when starting current, draws in the core, closing the contacts of the starting winding. When the engine speed increases and the current drops, the core, under the influence of gravity (or a spring), returns to its original position, opening the circuit.
Posistor relays, or PTC relays, are simpler and more reliable. Inside the case there is a ceramic element (posistor), which, when voltage is applied, heats up and sharply increases its resistance, actually breaking the starting winding circuit. After cooling (usually 2-3 minutes), the posistor is ready for use again. Such devices do not have moving mechanical parts, which makes them less sensitive to vibration, but they require time to cool down between startup cycles.
Relays may also differ in the method of mounting and the number of contacts. There are models with one contact, two, three and even four. The presence of additional contacts is often associated with the connection of a capacitor or additional protection circuits. When looking for a replacement, it is important to take into account not only the electrical parameters, but geometric dimensionsas well as the location of the terminals so that the device physically fits on the pins of the compressor.
Modern compressors are often equipped with universal relays that are suitable for a wide range of powers. However, for old Soviet refrigerators or specific models (for example, Liebherr or Electrolux), original components with special current cut-off characteristics may be required. An attempt to install a relay from a powerful two-compressor unit on a low-power single-chamber refrigerator can lead to the fact that the starting winding will not turn off in time and will burn out.
Key parameters for selecting an analogue
The most important parameter when looking for a replacement is the rated current. Each relay is marked on the body indicating the operating current for which it is designed. For example, the numbers 1/4, 1/5, 1/3 or values in amperes (1.3A, 2.5A) indicate at what current the relay should open the starting winding circuit. If you install a relay with a lower current, it will open the circuit too early and the compressor will not start. If it is large, the starting winding will work too long and overheat.
The second important aspect is the coil voltage (for electromagnetic relays). It must correspond to the mains voltage, that is, 220V. The type of compressor is also taken into account: for low-voltage refrigerators (car or marine), special relays for 12V or 24V are needed. Using a 220V household relay in a low-voltage circuit will result in the coil simply not working.
Installation orientation also matters. Some relays have an arrow UP or TOPindicating that they should be installed strictly vertically. This is especially true for induction models, where the core must move freely under the influence of gravity. PTC relays are less demanding in terms of orientation, but manufacturers still recommend maintaining the correct position for better heat dissipation.
Compatibility table and popular analogues
There are many manufacturers on the aftermarket that produce interchangeable components. Brands such as Danfoss (now Secop), Indesit, Ariston, Whirlpooloften use third party relays such as RT, CSR, PTC. Below is a table to help you navigate the markings and possible replacements.
| Original marking | Type | Operating current (A) | Possible analogue | Note |
|---|---|---|---|---|
| RT (Danfoss) | Induction | 1.2 - 2.5 | CSR, PTC (with adapter) | Requires precise current selection |
| PTC 110 | Posistor | 1.0 - 1.4 | PTC 111, PTC 112 | Universal solution |
| 380424 | Posistor | 1.3 | PTC 110, PTC 111 | Often installed on Indesit |
| 107160 | Induction | 2.2 | RT-2 | For powerful compressors |
It is important to understand that direct replacement of the induction relay with a posistor (and on the contrary) is not always possible without modifying the circuit. PTC relays often come complete with an adapter frame that allows them to be installed in place of induction ones. However, in some circuits with a protective relay-heater there may be connection nuances. Always check the connection diagram on the new device with the one on the old one.
If you do not find an exact match according to the markings, you can use the selection rule based on compressor power. For low-power units (up to 1/6 hp), relays with a current of 1/5 - 1/6 A are suitable. For medium-sized units (1/4 - 1/3 hp) - 1/4 - 1/3 A, respectively. Critical it is important not to install a relay with a cut-off current higher than the rated current of the compressor by more than 10-15%. This may result in the relay not turning off the starting winding in time.
Instructions for replacing the starting relay
The process of replacing a relay does not require complex tools, but requires compliance with safety precautions. Before starting any work, be sure to disconnect the refrigerator from the power supply. Unplug the plug from the socket. Even if the compressor is not running, dangerous voltage may remain in the circuit.
Remove the rear protective panel of the refrigerator to gain access to the compressor. It is usually secured with latches or several screws. You will see a black cylindrical or pear-shaped compressor tank, and on the side or bottom there is a plastic box to which the wires fit. This is our desired relay. Carefully remove the retaining bracket or strip holding the relay to the compressor pins.
☑️ Preparing to replace the relay
Before disconnecting the wires, take a photo or a detailed connection diagram. Wire colors may vary between models and cannot be confused. Typically, terminals are used that are simply removed by hand or with pliers. Some wires may be twisted and insulated with cambric - in this case, they need to be carefully separated and the ends stripped for a new connection.
Install the new relay on the compressor pins. Make sure it fits snugly and all the way. Connect the wires according to your diagram or photo. Check that the connections are secure: the wires should not dangle or touch hot parts of the compressor. Secure the relay with the retaining strip. Put on the protective cover and plug in the refrigerator. After a few seconds, a characteristic start-up click should be heard, and the compressor will start working smoothly, without humming.
⚠️ Attention: If you are changing the type of relay (for example, from inductive to posistor), make sure that the capacitor (if it was in the circuit) is connected correctly or removed if the new design requires it. An error in connecting the capacitor can lead to an explosion.
Common mistakes during self-repair
One of the most common mistakes is an attempt to “revive” an old relay by stripping the contacts or tapping. In modern sealed enclosures this is impossible, and in old ones such a measure gives only a temporary effect. The contacts will still burn out again, often after just a few switching cycles. In addition, a violation of the contact geometry changes the gap, which disrupts the current cut-off setting.
Another mistake is ignoring the compressor condition. If the refrigerator has been standing for a long time, condensation may have formed in it or oil may have become coked. Replacing the relay in this case will not help, but will only lead to the burning of the new part. Before installing a new relay, it is useful to “ring” the compressor windings with a multimeter to ensure their integrity and the absence of a short circuit to the housing.
Also, self-taught craftsmen often neglect the insulation of the wire connections. The vibration of a running compressor can quickly loosen a bad splice, causing sparking, heating and possible fire. Use high-quality terminal blocks or solder the connections securely, insulating them with heat shrink. Simple electrical tape dries out over time from the heat and can slip.
Is it possible to start a refrigerator without a relay?
Theoretically, you can start a compressor without a starting relay by applying voltage to the starting winding manually for a short time, but this is extremely dangerous and requires skills. For constant operation of the relay, it is necessary: without it, the compressor will not be able to pick up speed on its own and will burn out in a few minutes.
FAQ: Frequently asked questions
Is it possible to use a relay from another brand of refrigerator?
Yes, it is possible if the electrical parameters (current, voltage) and geometric dimensions match. The brand of the refrigerator (Indesit, Samsung, Bosch) is not as important as the brand and characteristics of the compressor itself (Danfoss, Embraco, Aspera). The main thing is that the relay is suitable in terms of cut-off current and type (induction or posistor).
Why did the new relay burn out a week after replacement?
There may be several reasons: the relay current is incorrectly selected (too large or small), the compressor itself is faulty (interturn short circuit, wedge), or problems with the voltage in networks. It is also worth checking the capacitor: if it is broken, it could also damage the new relay.
What is the difference between 1/4 and 1/3 relays?
The numbers indicate the approximate compressor power in horsepower for which the relay is designed. Relay 1/3 is designed for more powerful motors and has a higher operating current. Installing a 1/3 relay on a weak compressor (designed for 1/4) can lead to the fact that the starting winding will not turn off, which will cause it to overheat.
Is it necessary to change the thermal fuse along with the relay?
It is advisable, but not necessary. If the thermal fuse (heater) is visually intact and “rings” when dialed, you can leave it. However, if the relay burned out due to an overload, the heater could experience extreme heat and its performance could change. Ideally, change the pair.