Failure of the start-up relay - one one of the most common reasons why the refrigerator stops freezing. If you hear a characteristic clicking sound, the hum of the motor, which then suddenly stops, or the compressor does not start at all, the problem most likely lies in this unit. Replacing a part does not require calling a technician if you have minimal skills in working with electricians and tools.
In this article we will look in detail at how to make a relay for the refrigerator with your own hands, choosing the correct analogue or restoring the functionality of the old device. It is important to understand that this element is responsible for supplying voltage to the motor windings and protecting against overheating, so installation errors are unacceptable. We will look at the types of devices, the diagnostic algorithm and the step-by-step replacement process.
Before starting any work, you must completely de-energize the unit. Unplug the power cord from the outlet, move the refrigerator away from the wall and gain access to the bottom of the cabinet where the compressor is located. Only after this can you begin to visually assess the condition of the wiring and the relay itself.
What is a start-up relay and how it works
The start-up relay is an electromechanical device that is installed directly on the compressor housing. Its main task is to briefly supply current to the starting winding of the motor to create torque, and after the rotor accelerates, to turn off this winding. In parallel with this, the device performs the function of thermal protection, opening the circuit when the temperature or current increases critically.
The principle of operation depends on the type of design. Induction models use a coil, which, when current passes, creates a magnetic field that draws in the core and closes the contacts. Thermal relays (RTR) use a bimetallic plate that bends when heated. Modern models often combine both functions, being start-protective start-protective devices
A malfunction of this unit leads to the fact that the compressor either does not start at all, or operates in short jerks, after which the protection is triggered. If you ignore these symptoms, you can bring the engine to interturn short circuitwhich will require replacing the entire compressor, and this is much more expensive and complicated.
⚠️ Attention: Never try to start the compressor bypassing the relay by applying voltage directly to the starting winding for longer 2-3 seconds. This is guaranteed to lead to burning of the motor windings.
Diagnostics and signs of malfunction
Before looking for a replacement, you need to make sure that the problem is in the relay, and not in the compressor or wiring itself. The first sign of a malfunction is a characteristic sound: the refrigerator hums for 3-5 seconds, then a loud click is heard, and there is silence. After some time, the cycle repeats. This means that the trigger mechanism does not operate and the engine cannot go into operating mode.
For accurate diagnostics, the relay must be removed from the compressor. Carefully disconnect the wire connectors and remove the retaining bracket or bar. Visually inspect the body: the presence of melts, cracks or traces of burning indicates that the part requires replacement. Inside there may be carbon powder from a burnt tablet (in posistor models) or oxidized contacts.
If there is no external damage, you can ring the device with a multimeter. In normal condition, the resistance between the contacts should be zero (closed) or match the resistance of the coil. Infinite resistance or, conversely, a short circuit where it should not be, indicates a breakdown. Also check thermal relay for the integrity of the bimetallic plate.
- 🔊 Sound indication: frequent clicks every few minutes when the fan is running.
- 🔥 Heating: the relay is getting very hot or has a burning smell when touched.
- 🚫 No startup: the compressor is silent, although the current is flowing to it.
- 📉 Jumps voltage: the light in the refrigerator blinks when it tries to start.
Often the cause of failure is not the relay itself, but wear of the compressor. As a motor ages, it draws more starting current, causing overload and failure of the protection mechanism. Therefore, when installing a new relay on an old unit, be prepared for the fact that its operating life may be limited.
Choosing the type of relay to replace
The spare parts market offers many options, but not all of them are interchangeable. The key parameter is compressor power the type of refrigerant for which the system is designed. The relay is selected strictly for a specific engine model. Using an unsuitable analog will either make it impossible to start or cause the new part to burn out instantly.
There are several main series of start-up protection devices that are found in household refrigerators. The most common models are the RT (thermal) and RP (starting) series. For modern inverter and linear compressors, special electronic units are used, which cannot be repaired at home and are completely replaced.
When choosing, pay attention to the location of the contacts and the method of fastening. They can be vertical, horizontal or angular. The shape of the case and the presence of additional terminals for connecting the capacitor are also important. If you are not sure about the model, it is better to remove the old relay and look for an exact analogue by marking.
| Relay type | Principle of operation | Application | Features |
|---|---|---|---|
| RTK (Thermal). coil | Bimetallic plate | Old models (Atlant, Minsk) | Sensitive to overload |
| RP (Launch) | Electromagnetic coil | Single-phase compressors | Requires precise selection of current |
| Posistor | Crystal heating | Modern refrigerators | Simple design, no moving parts |
| Combined | Heat + Start | Universal use | Replaces two separate devices |
Important Please note that for compressors operating on refrigerant R600a (isobutane), relays with an intrinsically safe design are often required, since this gas is explosive. Such devices have special markings and a sealed housing.
Instructions for installing a new relay
The replacement process begins with dismantling the old part. Make sure the refrigerator is unplugged for at least 15-20 minutes to allow the capacitors to discharge and the compressor to cool. Remove the rear cover at the bottom of the unit by unscrewing the mounting screws. You will have access to the motor.
Carefully remove the retaining spring or bar that presses the relay to the compressor housing. Disconnect the wires by first photographing or sketching the connection diagram. Wire colors may vary depending on the manufacturer, so visual fixation will help avoid assembly errors.
Install a new relay on the compressor terminals. It should fit tightly, without play, but also without excessive force, which could break the ceramic motor leads. If the relay has three contacts, and you have two wires, the third contact (usually ground) can be left free, if this does not contradict the instructions for the specific model.
☑️ Relay replacement algorithm
After mechanical installation connect the wires to the terminals. Make sure the connections are secure and not loose. Vibration from a running compressor can loosen a poor connection, leading to sparking and further failure. Assemble the relay protective casing and secure it in its original place.
⚠️ Attention: Some relay models have a strict installation orientation (up, down or sideways). The case often has an arrow or the inscription "UP". Violation of the orientation can lead to incorrect operation of the thermal release.
Connection diagram and contact check
Correct connection is the key to successful repair. The standard circuit for a single-phase compressor includes a working winding, a starting winding and a common point. The relay is connected to the starting and working windings. If the system has a capacitor, it is usually connected in parallel to the starting winding through the corresponding relay terminals.
To check the correct assembly, you can use a multimeter in continuity mode. Ring the circuit from the refrigerator plug to the relay input - there should be contact. Then check the output from the relay to the compressor windings. The resistance between the contacts must correspond to the motor's nameplate data (usually from 10 to 30 Ohms for the working winding and more for the starting winding).
If you are using a universal relay, carefully study the markings on its body. Contacts can be designated by numbers or letters: S (Start) - start, R (Run) - work, C (Common) - general. By mixing up S and R, you will not be able to start the engine, and in the worst case, damage the windings.
What to do if the contacts do not fit?
If the terminals of the new relay do not match the pins of the compressor, do not try to bend them or extend wires unnecessarily. It is better to purchase an adapter block or find a relay of the exact series that fits “like original”. Using electrical tape near heating parts is dangerous.
After connecting all the wires, visually check the assembly again. There should be no exposed wiring anywhere that could touch the housing. Close the compressor with a protective casing, but do not screw the back wall of the refrigerator yet so that you can observe the first start-up.
Typical errors and safety measures
The most common mistake is ignoring the cause of the breakdown. If the relay burns out, then there was a reason: overload, power surge or compressor wear. By simply replacing a part, you may encounter a repeat of the situation in a week. After replacement, it is recommended to measure the current consumption of the compressor with a current clamp.
Another mistake is using a relay with a large power reserve “just in case”. This leads to the fact that the thermal protection does not operate on time, and the compressor operates in emergency mode, heats up and eventually burns out. Exact match motor parameters are critically important.
Do not forget about safety. Working with live electrical appliances is life-threatening. Carry out all manipulations to connect and disconnect wires only with the plug removed from the socket. Even after disconnection, a residual charge may remain in the capacitors.
- 🛡️ Insulation: use only heat-resistant insulation for wires near the compressor.
- 🔌 Grounding: do not ignore the ground contact, if provided by the design.
- 🌡️ Ventilation: make sure that installing a new relay does not block the air flow for cooling the motor.
- 🧹 Cleanliness: before installation, remove dust and dirt from the surface of the compressor so that they do not get inside the relay.
⚠️ Attention: If after replacing the relay the refrigerator works, but after a few hours it turns off again, the problem may be in the thermostat or a freon leak, and not in the electrics. Do not change the relay indefinitely if the cause has not been eliminated.
Frequently asked questions (FAQ)
Is it possible to repair an old relay rather than buy a new one?
In most cases, repair is impractical. If the coil burns out inside or the bimetallic plate is deformed, it is impossible to restore the factory settings. Cleaning the contacts may help temporarily, but the reliability of such work will be low. For posistor models, repair is excluded, since the ceramic element burns out.
Why does the new relay burn out immediately after installation?
This indicates a malfunction of the compressor itself. Most likely, an interturn short circuit has occurred in the motor windings, and the current consumption exceeds the permissible limit. The cause may also be jamming of the piston group. In this case, it is necessary to replace the compressor or the entire refrigerator.
How to determine the power of the compressor for selecting a relay?
The power is indicated on the nameplate (metal sticker) on the compressor body. Look for values in watts (W) or amperes (A). Also, the power is often encoded in the markings of the relay itself. If the nameplate is not readable, you can focus on the volume of the fridge compartment and the engine model.
Is a relay from another brand of refrigerator suitable?
Yes, if the electrical characteristics (operation current, power) and the geometric dimensions of the seat match. The brand of the refrigerator (Indesit, LG, Bosch) is secondary, the main thing is the brand and model of the compressor (Danfoss, Embraco, Secop) installed inside.