Sudden failure of the refrigerator often becomes an unpleasant surprise, especially when perishable products remain in the chamber. In most cases, the reason lies not in complex electronics or a freon leak, but in the failure of a small but critical component - start relay. It is this part that is responsible for starting the compressor, ensuring that voltage is supplied to the motor windings at the right moment.
If you notice that your refrigerator hums, but does not start, or the compressor clicks and immediately turns off, there is a high probability that the problem is in this particular unit. Fortunately, in 80% of cases refrigerator relay repair you can do it yourself, without resorting to the expensive services of a service center. This requires only a minimal set of tools and a basic understanding of the principles of operation of electrical equipment.
In this article we will analyze in detail the device of the starting mechanism, methods for its diagnosis and replacement algorithm. You will learn how to distinguish a relay failure from a breakdown of the compressor itself and what safety measures must be taken when working with high voltage. Correct diagnosis will help save budget and time.
⚠️ Attention: All repair work on electrical equipment must be carried out only after the device has been completely disconnected from the electrical network. Residual voltage in capacitors can be dangerous.
Design and principle of operation of the starting relay
The starting relay is an electromechanical device that temporarily connects the starting winding of the compressor motor. At the moment of startup, the refrigerator requires significant torque, which is provided by this particular winding. As soon as the motor rotor reaches the required speed (approximately 75% of the rated speed), the relay automatically opens the starting winding circuit, and the motor continues to operate on the main one.
There are two main types of such devices used in household appliances. The first type is induction (electromagnetic) relayswhich are more often found in old Soviet-made models and some modern budget lines. Their operation is based on a magnetic field created by the current in the winding, which draws in the core and closes the contacts. The second type is posistor (thermal) relayswhich are widely used in modern branded technology Indesit, Atlant, Beko.
The operating principle of a posistor is based on changing the resistance of a special ceramic element when heated. In a cold state, the resistance is minimal, current flows freely through the starting winding. The passing current heats up the posistor, its resistance increases sharply, and the circuit actually breaks. This process takes a split second, but it ensures a smooth and reliable start of the motor.
Why does the relay burn out?
Frequent power surges in the network, long power outages or natural wear of the contacts lead to the fact that the relay ceases to perform its function. In posistor models, the ceramics can crack, and in induction models, the contacts can burn or the core can stick.
Main symptoms of relay malfunction
You can determine that it is the trigger mechanism that has failed by the characteristic signs that appear during operation of the unit. Owners often confuse these symptoms with a breakdown of the compressor itself, which leads to erroneous diagnosis and unnecessary costs. Accurate identification of the problem is half of a successful repair.
The most obvious sign is the situation when Compressor hums but will not start. You hear a characteristic low-frequency hum that lasts 3-5 seconds, after which a click is heard and the engine stops. After some time (from 30 seconds to several minutes), the cycle repeats. This indicates that the start winding is not getting a pulse or is not turning off in time.
Other common symptoms include:
- 🔊 Frequent clicks: Sounds coming from the back of the refrigerator at intervals of several minutes, indicating attempts to start.
- 🔥 Case heating: The compressor becomes hot to the touch, although the refrigerator does not cool, which indicates operation in short circuit or overload mode.
- ❄️ Lack of cold: In the chambers the temperature is equal to room temperature, despite the fan running (in No Frost models) and burning light.
In some cases, during disassembly, you may find that the relay has a melted body or emits an unpleasant burning smell. This is a sure sign that a breakdown or short circuit has occurred inside. If you smell a burnt plastic smell coming from the rear panel, stop using the device immediately.
Diagnostics: how to check the relay multimeter
Before buying a new part, you need to make sure it is faulty. To do this, you will need a simple multimeter (tester) configured for resistance measurement mode (Ohm). Diagnostics allows you to avoid purchasing unnecessary spare parts if the problem lies, for example, in broken wiring or stuck contacts.
First you need to remove the relay. It is usually mounted on the side of the compressor and covered with a plastic or metal casing. Carefully remove the cover, disconnect the terminals and remove the device. A visual inspection can immediately give an answer: cracks, blackening or a burning smell indicate the need for replacement.
Checking the induction relay:
- 📏 Checking the contacts: In a horizontal position, the contacts should ring (resistance is close to zero).
- 🔄 Checking the coil: The winding resistance should be within normal limits (usually 30-150 Ohms), the absence of resistance indicates a break.
- ⬆️ Orientation: When the relay is turned over, the contacts should open (infinity resistance), which simulates operation under the influence of gravity.
Checking the posistor relay:
In a cold state, the resistance of the posistor should be 10-60 Ohms. If the multimeter shows one (infinity) or zero, the part is faulty.
Preparation for replacement and selection of spare parts
If the diagnostics confirm the malfunction, you need to purchase a new analogue. The market offers many options, but it is important to choose a part that is compatible with your compressor model. There are no universal solutions, since the starting current parameters and mounting geometry may differ from different manufacturers.
The relay body always has markings containing information about the manufacturer, type and electrical characteristics. The main parameters that you need to pay attention to:
| Parameter | Description | Where to find |
|---|---|---|
| Compressor model | For example, Danfoss TL4G, Secop, Aspera | Tag on the motor housing |
| Rated current | Current strength for which the relay is designed (for example, 1/4 HP, 1/5 HP) | Marking on the relay |
| Connection type | Number and location of pins (2, 3 or 4 contacts) | Visual inspection |
| Orientation | Vertical or horizontal position during operation | UP arrow on case |
When purchasing, pay attention to the country of origin. Original parts from Danfoss or Secop last longer than cheap Chinese counterparts, however, the latter often cost several times less and are also quite functional if used correctly. If you cannot find an exact analogue, you can use universal kits, but they require more complex setup.
⚠️ Attention: Compressor specifications and relay compatibility may vary depending on the model year. Before purchasing, check the markings on the old part with the seller's catalog data or the manufacturer's official documentation.
Step-by-step instructions for replacing the relay
The process of replacing the starting relay does not require specialized equipment other than a screwdriver and possibly pliers. The main thing is to act carefully so as not to damage the compressor tubes and electrical wires. The whole process takes from 15 to 30 minutes.
Action algorithm:
- Unplug the refrigerator and move it away from the wall, providing access to the rear panel.
- Remove the protective cardboard or metal cover at the bottom of the rear wall that covers compressor.
- Take a photo of the wire connection diagram so as not to confuse them during assembly.
- Carefully remove the old relay from the compressor contacts. It may fit tightly, so rock it slightly from side to side.
- Disconnect the wires from the old relay (if they are not on a common block) and transfer them to the new device, observing polarity and location.
- Install the new relay on the compressor fittings until a characteristic click is heard.
☑️ Replacement checklist
Pay special attention to the orientation of the part. There is often an arrow on the case with the inscription UP or TOPwhich indicates which side of the relay should face up. Incorrect installation of the induction relay will result in it not opening the circuit, which can burn the motor windings.
After installation, reassemble the structure in the reverse order, but do not tighten the back cover completely yet. Plug in the refrigerator and listen. Startup should be quiet, without buzzing or clicking. If the motor is running smoothly, you can fix the cover and push the unit into place.
Common mistakes and precautions
Even with instructions, beginners often make mistakes that can lead to repeated breakdowns or damage to the equipment. Avoid rushing and ignoring little things that at first glance seem insignificant.
One of the common mistakes is replacing the relay without checking the compressor itself. If the motor is “jammed” (mechanical failure inside), then the new relay will burn out after a few seconds of operation, since the current in the jammed motor will be prohibitive. Therefore, if after replacement the situation has not changed, the problem is deeper.
Other typical errors:
- 🔌 Bad contact: Loose terminals cause sparking and heating, which will quickly damage the new part.
- 🌡️ Ignoring overheating: If the refrigerator is standing close to each other to the wall, heat exchange is disrupted, and the thermal relay will operate constantly, even if it is working properly.
- 🧹 Dirt and dust: A condenser clogged with dust (grid at the back) increases the load on the compressor, shortening the service life of all electrical components.
⚠️ Attention: Never try to “revive” the relay by tapping or briefly closing the contacts. This can lead to a fire or electric shock.
Is it possible to use a relay from another model?
In emergency cases, installing an analogue with similar characteristics is allowed if the mounting location and rated current are the same. However, using a non-standard part is a temporary solution, and it is better to order the original.
Prevention and extension of service life
In order for the new unit to last a long time, it is necessary to provide the refrigerator with the correct operating conditions. Stable voltage in the network is the main friend of your equipment. Voltage surges destroy not only relays, but also electronic control modules.
It is recommended to use a surge protector or voltage stabilizer, especially in old houses or in rural areas. It is also important to regularly, at least once a year, inspect the back of the refrigerator: remove dust from the condenser and check the integrity of the wire insulation.
Timely replacement of the start relay is not only savings on compressor repairs, but also a guarantee of food safety. Remember that a working refrigerator is quieter and consumes less electricity, since it does not waste resources on constant attempts to start.
Can a burnt relay be repaired or just replaced?
In most cases, a relay is a disposable device, especially posistor models. Attempts to disassemble and clean contacts in induction relays give only a temporary effect, since the calibration of the spring and the accuracy of operation are disrupted. Replacing with a new part is the only reliable solution.
Why does the new relay burn out immediately after installation?
This indicates a more serious problem. Most likely, the compressor itself is faulty (inter-turn short circuit of the windings or wedge of the piston group). Also, the cause may be a malfunction of the protective thermal relay, which does not turn off the power when overloaded, or problems with the wiring.
What is the difference between relays for No Frost refrigerators and a conventional drip system?
There is no fundamental difference in the design of the starting relay itself, since it works in conjunction with a compressor. The difference may be in the mounting method, the presence of additional fan connectors (in rare cases) or the shape of the case, depending on the refrigerator model. It is important to select according to the marking of the compressor.
How much does it cost to replace a relay in a service compared to self-repair?
Independent replacement will cost you only the cost of the part (from 500 to 2000 rubles). At the service center, the cost of the repair part will be added to the cost of the technician and the visit, which can ultimately amount to from 2,500 to 5,000 rubles, depending on the region and model of the refrigerator.