Independent repair of a refrigerator often seems like a difficult task for owners, requiring special education, but replacing the main components of the temperature control system is quite within the capabilities of a person with basic skills in working with tools. Thermostat i start relay —these are two elements whose failure most often leads to the compressor stopping or, conversely, to continuous operation of the unit without shutting down. Understanding the principle of their operation and the sequence of actions when replacing will help save a significant amount on calling a technician.
Before you start disassembling, you need to clearly understand that you will be working with electric shock and refrigerant, therefore ignoring safety rules is unacceptable. Refrigerator must be completely de-energized, and all manipulations with the wires are carried out only after removing the plug from the socket. In this article, we will analyze an algorithm of actions that will allow you to safely diagnose a malfunction and install new parts, restoring the equipment to working order.
However, it is worth considering that the design of refrigeration units from different manufacturers may differ significantly.
⚠️ Attention: Wire connection diagrams in new electronically controlled models may differ radically from classic mechanical systems, so always check the technical documentation of your device.If you are not confident in your abilities or see complex electronic boards instead of simple terminals, it is better to stop at the diagnostic stage.
Diagnostics of thermostat and relay malfunctions
Before buying new spare parts, you need to make sure that the problem lies precisely in them, and not in the compressor or freon leak. Thermoregulator (thermostat) is responsible for turning the motor on and off depending on the temperature inside the chamber. If it fails, the refrigerator may either not start at all or work without interruption, causing severe freezing of the evaporator. Start relay, in turn, ensures the engine starts and protects it from overloads; its breakdown is often accompanied by a characteristic click and failure to start the compressor.
For an initial check of the thermostat, you can use a simple test method with a multimeter in resistance measurement mode. At room temperature, the contacts of a working mechanical thermostat should be closed, showing zero or a value close to it on the device screen. If the device shows an open circuit (one or infinity), it means that the circuit is broken and temperature regulator requires replacement. It is also worth paying attention to the capillary tube: it should not have any kinks or damage.
Checking the start relay requires visual inspection and acoustic analysis. Often you can hear rattling inside the plastic case, which indicates destruction of the core or contacts.
⚠️ Attention: When checking the relay, do not try to disassemble its case if it is soldered or glued - this will break the tightness and make the part unsuitable for further use.The best diagnostic method is to install a known-good analogue, but for this you need to know the exact markings.
Symptoms of faults often overlap, so it is important to analyze the behavior refrigerator in the complex. Below is a table that helps differentiate problems:
| Symptom | Probable cause | Action |
|---|---|---|
| The refrigerator hums, but does not start | The starting relay is faulty or the compressor is jammed | Replacing the relay, checking the compressor |
| The compressor runs constantly, there is no cold | Freon leak or the thermostat is faulty | Checking the thermostat, calling a technician |
| The refrigerator does not turn on at all | Open circuit of the thermostat or lack of power | Thermostat check, checking the socket |
| Frequent clicks when trying to start | The starting relay or thermal relay has burned out relay | Replacement of the protection relay |
Necessary tools and preparation of the workplace
High-quality repairs are impossible without a suitable tool, which should be on hand before starting work. You will need a set of screwdrivers (flathead and Phillips), since the mounting screws from different manufacturers may differ in the type of slot. Indispensable multimeterfor working with electrical contacts, allowing you to check the integrity of circuits and the presence of voltage. Also prepare pliers with insulated handles and side cutters to carefully cut the wires, if necessary.
Particular attention should be paid to the organization of the workspace. Refrigerator it must be moved away from the wall, providing access to the back wall where the compressor is located. It is better to cover the floor in the work area with dry rags or cardboard so as not to damage the floor covering and not to lose small parts that may fall. It is critically important to completely defrost the unit before starting work if ice has formed in the system, since water can get on the electrical contacts.
For a safe connection For wires, prepare high quality insulating tape or heat shrink tubing. The use of ordinary low-quality insulating tape is unacceptable, since the temperature in the compressor area may rise, which will lead to melting of the insulation and a short circuit. Terminal blocks or special connectors will also be useful for creating reliable contact without twists.
Don't forget about lighting. The compressor area is often dark, so a headlamp or high-powered clip-on lamp can help you see part markings and wire condition. Working by touch in the dark is dangerous and ineffective.
Removing the old thermostat: step-by-step algorithm
The process of removing the thermostat begins with finding its location. In most models of Atlant, Indesit or Stinol refrigerators, it is located inside the refrigerator compartment, and its adjustment knob is located on the control panel. First, you need to remove the regulator handle by pulling it towards you and unscrew the fastening screw, if there is one under it or under the decorative trim.
After removing the fasteners, carefully remove the thermostat housing from the niche. Capillary tube, which comes from the sensor, is usually fixed in special grooves on the chamber wall or evaporator. It must be released very carefully, being careful not to bend or damage the thin copper tube, as this will lead to leakage of sensitive liquid and failure of the new part. Thermostat can be attached to latches that require careful pressing with a flat-head screwdriver.
Features of fastening the capillary tube
The capillary tube should not have sharp creases. When installing a new thermostat, it must be laid exactly along the same route as the old one, secured in standard clips. The excess length of the tube is neatly rolled into a ring, but not cut off.
When the housing is removed, we move on to the electrical part. Take a photo of the location of the wires before disconnecting them - this will become your main cheat sheet when connecting a new part. Disconnect terminals by marking them with a marker or using color coding. Usually the wires are color coded, but over time it can fade or become dirty.
If the thermostat is located outside (on the back wall in older models), it is accessed by removing the compressor protective casing. In this case, the procedure is simplified to unscrewing a few screws and disconnecting the contact group. The main thing is not to lose the fasteners, since the vibration of the compressor can loosen poorly fixed parts.
Replacing the compressor starting relay
The starting relay is located directly on the compressor housing and is covered with a protective plastic or metal casing. To access it, you need to unscrew the screws securing the casing or loosen the clamp, if provided by the design. After removing the protection, you will see a black cylindrical or rectangular block placed on three pins coming out of the compressor.
Removing the relay requires caution. It may be a tight fit, so gently wiggle it from side to side while pulling upward to avoid breaking the plastic clips or damaging the contacts. On the bottom of the relay there is often an arrow indicating the "Up" position or a marking that must be remembered for proper installation of the new part. Do not use excessive forceso as not to break the plastic clips or damage the contacts. The bottom of the relay often has an arrow indicating the "Up" position or a marking that you need to remember to install the new part correctly.
☑️ Check before installing the relay
The new relay is installed in the reverse order. It is important that it sits tightly on the pins and all the way. If the relay has additional wires (for example, for a fan or a second winding in dual-compressor models), their connection must strictly comply with the diagram. Thermal relay, which is often built into the starter or located nearby, is also checked for the integrity of the bimetallic strip.
After installing the casing, make sure that that the wires are not pinched and do not touch the hot parts of the compressor. The vibration of a running motor should not rub against the insulation of the wires, so if necessary, use plastic ties to secure the harnesses.
Wire connection diagram and color code
The most critical step is connecting the electrical wires to the new thermostat. An error here may result in a short circuit or damage to the compressor. The standard color marking of wires in refrigerators is as follows, however, manufacturers may deviate from these standards, so visual verification is required.
Usually three main wires are used: brown (or black) is the phase coming from the plug; blue (or white) - zero; and yellow-green - grounding. Thermostat contacts often marked with numbers or letters. For example, pins “3” and “4” are the main power circuit for the compressor, and pin “6” can go to a light bulb or fan. Connection diagram should always take priority over the color coding of the wires.
If you change a domestic TAM thermostat to an imported analogue (or vice versa), the numbering of the contacts may not match. In such cases, you need to use a multimeter to determine which contacts are closed when you turn the knob.
⚠️ Attention: Never connect wires using simple twisting without subsequent soldering or using terminals. The vibration of the refrigerator will quickly loosen the twist, which will lead to sparking and fire.
For convenience, use the following correspondence table, but remember that it is for reference only:
| Function | Wire color (standard) | Contact on thermostat |
|---|---|---|
| Phase (input) | Brown / Red | Input terminal |
| Phase (to compressor) | Black / White | Output terminal |
| Ground | Yellow-green | Case / Ground terminal |
| Lamp / Fan | Blue / Orange | Add. contact |
Testing and first launch of the system
After all the parts are installed, and the wires are connected and insulated, do not rush right away load the refrigerator with food. The initial startup should take place in idle mode. Plug in the unit and listen to the sounds. The compressor should start a few seconds after the characteristic click of the relay.
Check the operation of the thermostat. Set the regulator knob to the middle position and note the operating time of the compressor. It should turn off when the temperature in the chamber reaches the set value. If the motor runs continuously for more than an hour and does not turn off, and there is no uniform layer of frost on the evaporator (or it appeared only at the entrance of the tubes), perhaps the thermostat does not sense the temperature or is installed incorrectly.
Pay attention to the heating of the compressor housing and relay During the first hours of operation, they may heat up, but should not be hot. Start relay should not make any extraneous sounds, crackling or buzzing. If you hear frequent clicks (turning on and off every 10-20 seconds), this is a signal of a faulty relay or problems with the motor windings.
Leave the refrigerator turned on for 5-6 hours without loading. During this time, it should reach operating mode and freeze the water in the freezer. Only after making sure of stable operation and the absence of leaks or burning smells can you begin operation as usual.
Is it possible to install a thermostat with other parameters if the original is not for sale?
Yes, you can, but you need to follow a few rules. The length of the capillary tube should be no less than that of the original (the excess can be carefully rolled into a ring). The temperature response range should be close to the original (usually indicated on the case, for example, -12...-20°C for a freezer). Setting a thermostat with a shutdown threshold that is too low will result in the compressor running non-stop.
Why does a new relay burn out a week after replacement?
Most often this is due to a malfunction of the compressor itself. If the motor windings have an interturn short circuit or increased resistance, the starting current exceeds the rated current and the relay burns out. Also, the cause may be incorrect installation of the relay (upside down) or poor contact in the power circuit.
Is it necessary to charge freon after replacing the thermostat?
No, when replacing the thermostat and start relay, the cooling system (pipes and compressor) is not opened, so the refrigerant remains inside. Freon needs to be charged only if you accidentally damaged the capillary tube of the thermostat or other elements of the system during installation.
How to distinguish a starting relay from a thermal one?
A starting relay usually has a more complex internal structure with a coil or posistor and is placed on three pins of the compressor. A thermal (protective) relay is often a tablet or bimetallic strip in a separate housing or built into the overall structure, and it responds specifically to current and heat, opening the circuit when overloaded. In modern assemblies, they are often combined into one block.