A sudden stop of operation of the refrigerator or characteristic clicks when trying to start the compressor often indicate a faulty start relay. This small but critical device is responsible for starting the engine and protecting it from overheating. If you are faced with such a problem, replacing the relay yourself can be a quick and economical solution that allows you to return the equipment to life without calling a technician.
In this article we will look in detail at how to properly connect the relay in the refrigerator to avoid a short circuit or repeated breakdown of the compressor. You will learn about the differences between induction and posistor models, learn how to check the performance of parts and understand the nuances of connection depending on the brand of the unit. Safety and accuracy actions here play a decisive role.
Before you start working, you need to understand that a relay is not universal part. Starting relay selected strictly for a specific model of the compressor, and not the refrigerator itself. An error in selection or incorrect installation can lead to burnout of the motor windings, so carefully study the information below before starting repairs.
Design and principle of operation of the starting relay
The starting relay is an electromechanical or electronic switch that briefly supplies voltage to the starting compressor winding. When the refrigerator is turned on, the motor rotor is motionless, and a powerful impulse is required to spin it up. As soon as the shaft reaches the required speed, the relay opens the starting winding circuit, and the engine continues to operate on the main winding.
In modern models, they are most often found posistor relays, where the role of the switch is performed by a thermistor (posistor). When current is applied, it heats up, its resistance increases sharply, and the starting winding circuit actually breaks. Older models can be equipped with induction relays with a movable core that closes contacts under the influence of a magnetic field.
The difference between induction and posistor relays
Induction relays have a movable mechanical core that can stick or wear out. PTC (solid-state) devices have no moving parts, they simply change resistance when heated. Replacing one type with another is possible only if the electrical parameters and seats are fully compatible.
In parallel with the starting function, also thermal protectionis often implemented. A bimetallic plate is built into the relay housing or separately from it, which opens the circuit when the compressor overheats critically. This prevents melting of the winding insulation and failure of the expensive motor.
Diagnostics: how to understand that the relay is faulty
Before changing the part, you need to make sure the diagnosis is correct. Symptoms of a faulty relay are often confused with a breakdown of the compressor or thermostat itself. The main sign is a characteristic sound: the refrigerator hums for a few seconds, then a loud click is heard, and there is silence. After some time, the cycle repeats.
Visual inspection can also provide a lot of information. If the relay body shows signs of burning, melted plastic, or blackened contacts, the device definitely requires replacement. Sometimes the problem lies in oxidation of the contacts, but in most cases it is easier and more reliable to install a new unit.
- 🔊 The compressor hums for 5-10 seconds, then clicks and turns off.
- 🔥 The relay body has traces of thermal effects or deformation.
- ❄️ The refrigerator has stopped freezing, and the light inside is on.
- ⚡ When checking with a multimeter, the contacts do not close or show high resistance.
For an accurate check, use a multimeter in resistance measurement mode. Posistor in a cold state it should have a low resistance (several tens of Ohms). If the device shows one or infinity, the part is faulty. Also check the integrity of the bimetallic thermal protection plate - it should “ring” short.
Preparation for replacement and selection of a new part
The most important stage is the correct selection of spare parts. Relays are marked not only by the refrigerator brand (for example, Indesit, Atlant, Bosch), but also by the compressor model. There are always markings on the body of the old relay that need to be copied or photographed. Ignoring this step may result in purchasing an incompatible component.
Before starting work, be sure to turn off the power to the refrigerator by unplugging the plug from the outlet. You will need a minimum set of tools: flat and Phillips screwdrivers, pliers and, preferably, a multimeter for the final check. Also prepare a dry rag to clean the contacts from dust and oxides.
☑️ Preparing to replace the relay
Pay attention to the installation orientation. The relay body often has an arrow or inscription TOPindicating the top position. Posistor relays are sensitive to spatial position, and installing them upside down can disrupt the operation of the cooling system or lead to rapid failure.
⚠️ Attention: Never replace electrical components while the refrigerator is connected to the network. Even after disconnecting, give the capacitors (if they are in the control circuit) a few minutes to discharge, although in older models with mechanical control this is less important.
Step-by-step instructions: how to remove the old relay
The dismantling process begins by removing the rear protective panel at the bottom of the refrigerator. It is usually secured with latches or several screws. After removing the cover, you will see the compressor - a black metal “tank”, from which copper tubes and electrical wires extend.
On the shank of the compressor (usually on the left or right side) there is a plastic box - this is our desired relay. It fits directly onto the three pins of the compressor and is secured with a metal bracket or plastic clips. Carefully remove the fixing bracket, if there is one.
Remove the relay using careful rocking movements; do not pull by force, so as not to damage the wires or pins of the compressor. If a part has become stuck due to time and temperature, you can slightly warm it up with a hairdryer (not an open fire!), but usually a gentle force is enough. Disconnect the wires, first remembering or photographing their location.
Connection diagram: how to correctly install a new relay
Installing a new relay is done in the reverse order of removal. The main rule is the correspondence of contacts. On the inside of the relay and on the pins of the compressor there are markings: S (Start - starting winding), R (Run - working winding) and a common contact. In some models, there is no common contact as such; it is formed through the terminal block.
If you change the type of relay (for example, from induction to universal posistor), you may need the circuit included with the new part. Often the kit includes adapter wires or terminals. Connect the wires strictly by color, if they match the old circuit, or by terminal marking.
| Contact marking | Purpose | Wire color (typical) | Location on the compressor |
|---|---|---|---|
| C (Common) | Common phase input | Red / Brown | Lower left (conditionally) |
| S (Start) | Start winding | Black / Blue | Upper |
| R (Run) | Working winding | White / Green | Bottom right (conditionally) |
| GND | Grounding | Yellow-green | On the body |
After installing the relay on the pins, make sure that it is seated tightly and all the way. If a locking bar is used, return it to its place. Check to see if the structure is loose when slightly rocked. Loose contact will lead to sparking and re-burning of the part.
Checking functionality and first start
Before closing the back cover, perform a test run. Plug in the refrigerator. You should hear the compressor start confidently without a long hum before starting. After 10-15 seconds, the hum should become smooth and quiet, without extraneous clicks.
Feel the relay body (be careful, it may get hot). If it heats up evenly and does not emit a burning smell, and the compressor operates stably, it means connection diagram it is assembled correctly. Let the refrigerator operate for 15-20 minutes in open mode (without the back cover), monitoring the temperature of the condenser (grid at the back).
- 👂 The startup sound should be clear, without a lingering hum.
- 🌡️ The compressor should heat up moderately, and do not get hot.
- 💡 The light in the refrigerator should burn steadily, without blinking.
- 🔄 The on and off cycles should occur according to the thermostat timer.
⚠️ Attention: If after replacing the relay the compressor hums, but not starts, immediately unplug the refrigerator. This may mean that the problem is not in the relay, but in a jammed motor or an interturn short circuit. Further attempts to turn on may kill the compressor.
If everything went well, carefully arrange the wires so that they do not touch the hot copper pipes or moving parts, and install the protective back panel in place. Securely secure it with screws or latches.
What to do if the new relay also does not work?
If you installed a new, known-to-be-good relay, and the situation has not changed, the problem may be in the compressor itself (jamming) or in the wiring. Check the voltage at the relay input. If there is no voltage, look for an open circuit in the circuit to the relay. If there is, but there is no start, there is a high probability of motor malfunction.
Frequent errors and precautions
One of the most common mistakes is ignoring the reason for the failure of the old relay. If the relay burns out, it is often the result of a compressor overload, voltage problems or poor contact. By simply replacing a part, you can get the same breakdown in a month.
Also, technicians often forget to check the condition of the terminal block. If the contacts are oxidized or melted, they must be cleaned or replaced. Using electrical tape instead of heat shrink near a hot compressor is unacceptable - the insulation will melt, which will lead to a short circuit.
Do not try to repair a burnt-out relay by stripping the contacts or “witchcraft” with the spring. Relay is a consumable material with a calculated cycle life. A device restored by handicraft will be unstable and may cause a fire.
If your refrigerator is a model with an inverter compressor, there may not be a classic starting relay in its usual form. In such systems, starting is controlled by an electronic control unit. Trying to find and replace a mechanical relay there will lead to a dead end, since it simply does not exist.
Is it possible to install a relay from another refrigerator?
It is possible, but only if the electrical characteristics (operation current, type of compressor) and the geometric dimensions of the seat match. Universal relays often come with a set of adapters, which simplifies the task, but it is better to look for the original or a complete analogue by the catalog number.
Why does the relay burn out repeatedly (constantly)?
Frequent combustion of the relay indicates that the compressor is working in heavy duty: the condenser at the back is dirty, the thermostat is faulty (does not turn off on time), or the network voltage is constantly low. Also, the reason may be the loss of freon, due to which the motor does not cool and overheats.
How much does it cost to replace a relay with your own hands?
The cost of the relay itself varies from 300 to 1500 rubles, depending on the model and manufacturer. This is much cheaper than calling a specialist, whose work together with the spare part will cost 2,500–4,000 rubles. The main thing is to correctly diagnose the malfunction.
Is it dangerous to leave the refrigerator with the lid open?
For a short-term test (15-20 minutes) - it is acceptable if you monitor the process. However, operation without a cover is prohibited: dust, moisture and small objects will get inside, which can cause a short circuit or damage the insulation of the wires. In addition, the air flow for cooling the compressor will be disrupted.
Is it necessary to defrost the refrigerator before replacing?
There is no need to specially defrost the unit to replace the relay, since access to the compressor is from the bottom rear. However, if the refrigerator worked intermittently and a “fur coat” formed inside, it is better to let it stand turned off for several hours so that the moisture evaporates before turning on the electricity again.