A sudden stop of the compressor or, conversely, its continuous operation often indicates a malfunction in the temperature control system. If you notice that food has begun to deteriorate due to insufficient cooling, or a giant coat of snow has frozen over, the temperature relay becomes the first suspect. This small but critical element is responsible for turning the motor on and off depending on the readings of the temperature sensor. refrigerator compartment started to deteriorate due to insufficient cooling, or a giant coat of snow has frozen over, the temperature relay becomes the first suspect. This small but critical element is responsible for turning the motor on and off depending on the readings of the temperature sensor.
Many owners of household appliances rush to call a technician at the first sign of a malfunction, but basic diagnostics can be carried out independently. Understanding how it works thermostat will allow you to save time and money by determining whether the problem is actually mechanical or electrical. In this article we will analyze all the stages of inspection, from visual inspection to the use of measuring instruments.
Before you begin disassembling, you must ensure safety. Disconnect the unit from the power supply and prepare the workplace. It is important to understand that temperature relay is a mechanical or electronic device that wears out over time, and its replacement is a standard maintenance procedure.
Signs of a thermostat failure
Symptoms of thermostat failure are often disguised as other breakdowns, such as a freon leak or a compressor malfunction. However, there are characteristic signs that indicate problems with temperature sensor. If your refrigerator is behaving strangely, analyze its operation in recent days.
The most obvious signal is the lack of cyclical operation. The motor either does not start at all or hums continuously, trying to cool the chamber to impossible values. In the first case, the products melt, in the second, they freeze in an ice block, and a thick layer of frost forms on the walls.
It is also worth paying attention to the following manifestations:
- 🔌 The compressor does not turn on even after defrosting and restarting.
- ❄️ In the refrigerator compartment there is too much warm, despite the maximum setting of the regulator.
- 🧊 In the freezer, the food is covered with a crust of ice, and it is too cold inside the chamber.
- 💡 The lighting bulb is constantly on or does not light up (in some models the thermostat is connected to the lighting circuit).
Sometimes the cause is not a breakdown of the element itself, but and displacement of its rod or damage to the capillary tube. If you notice mechanical damage or traces of corrosion on the contacts, check with a multimeter the absence of a chain will show. In such cases, repair is usually impractical; replacement is required.
⚠️ Attention: If the refrigerator makes clicks when trying to start, but the motor does not start, this may indicate not only the relay, but also a malfunction of the starting relay or the compressor itself. Do not rush to change all the parts at once.
Preparation for diagnostics and dismantling
To carry out high-quality diagnostics, you need to gain access to the thermostat. In different models of refrigerators, be it Indesit, Atlant or Beko, the location of this element may differ. Usually it is located inside the refrigerator compartment, hidden by a plastic cover, or brought out in the form of an adjustment knob.
Before starting work, be sure to disconnect the device from the mains. This is a critical safety rule because you will be working with live electrical contacts. Also prepare the necessary tools: screwdrivers (Phillips and flat-head), pliers and a multimeter.
The dismantling process generally looks like this:
- 🔧 Remove the temperature control knob, if it is located on the panel (sometimes you need to remove the decorative plug).
- 🔩 Unscrew the mounting screws holding the plastic thermostat housing.
- 🔌 Carefully disconnect the electrical wires, having first memorized or photographed the connection diagram.
- 🧊 Remove the sensitive element (capillary tube) from the mounting hole in the evaporator.
Be extremely careful when removing the capillary tube. It is very thin and easily damaged. If there is ice inside the chamber, allow the refrigerator to defrost completely so as not to break fragile parts when removing it. Dismantling should be done without using excessive force.
☑️ Preparation for inspection
Visual inspection and initial check
After removal conduct a thorough visual inspection of the thermostat. Often external defects can indicate the cause of a malfunction without the use of complex instruments. Pay attention to the condition of the case: there should be no cracks, traces of melting or corrosion.
Pay special attention to the contact group. If you see black carbon deposits, oxides or traces of sparking on the contacts, this is a sure sign of poor contact. Such defects lead to heating and eventual failure of the entire control system. Cleaning the contacts may help temporarily, but it is better to replace the assembly.
Check the integrity of the capillary tube and bellows. If the tube has dents, creases, or, worst of all, traces of gas leaks (oily stains), the thermostat will not work. Tightness systems are the key to correct response to temperature changes.
Also inspect the wires going to the relay. The insulation must be intact, without cracks or melting. If the wires are frayed or twisted, this may cause a short circuit or open circuit. In such cases, it is necessary to restore the wiring before installing a new element.
Why do contacts oxidize?
Oxidation of contacts often occurs due to increased humidity inside the chamber or condensation on the electrical part of the thermostat. This creates resistance, which leads to heating and burning of the contacts, which ultimately disrupts signal transmission to the compressor.
How to check a thermostat with a multimeter
The most accurate diagnostic method is diagnosis contacts using a multimeter. This method allows you to determine with a high degree of probability whether the electrical part of the thermostat is working. To carry out the test, switch the device to resistance measurement mode (Ohm) or continuity mode.
First, determine which contacts are closed. In different models there may be two or three. Typically the pins are labeled 3-4, 3-6 or 3-4-6. If there is no marking, experimental selection will be required. The multimeter probes are connected to the contacts, and we observe the readings of the device.
The test algorithm is as follows:
- 📉 Set the regulator knob to the "Maximum" (or "6-7") position.
- ⚡ Attach the multimeter probes to contacts (usually 3 and 4).
- 🔊 If a beep is heard or the arrow deviates, the circuit is closed, the contacts are normal.
- 🌡️ Cool the sensitive element (put it in the freezer for 10-15 minutes) and check again - the circuit should break.
If the circuit does not break during cooling, it means the thermostat is “stuck” and requires replacement. If the circuit does not close even in a warm state, it means that the contacts have burned out or oxidized. Multimeter is a reliable assistant, but it is important to correctly interpret its readings.
For electronic thermostats (where instead of a knob there is a digital panel), testing the mechanical contacts is not fully applicable, since there the control goes through the board. However, checking the resistance of the temperature sensor (thermistor) is possible. The resistance should change with temperature changes.
Checking without a multimeter: traditional methods
What to do if there are no measuring instruments at hand? There is a method that allows you to check the functionality of the thermostat using only a low temperature. This method is less accurate, but often helps make a decision about the need for replacement.
The essence of the method is forced cooling of the sensitive element. If the thermostat is working properly, then when a certain temperature is reached it should break the circuit, and the compressor (if the circuit is assembled) will stop receiving power. However, when the relay is removed, we check the opposite - the circuit is closed when heated.
Here is what you can do:
- 🧊 Place the removed thermostat (or only its sensitive tube) in the freezer for 20-30 minutes.
- 🔌 After cooling, quickly connect the contacts (you can use a jumper made of wire) and connect the plug of the refrigerator.
- 🏃 If the compressor starts, it means that when heated to room temperature, the contacts should open (but we won’t see this without devices).
- 🔄 A simpler option: just short-circuit the wires going from the thermostat, among themselves. If the refrigerator works in normal mode, the problem is in the relay.
The thermostat may operate at -5°C instead of the required -14°C, and the refrigerator will not work correctly. Therefore diagnostics a multimeter is preferable.
⚠️ Attention: Do not leave the refrigerator turned on with the thermostat contacts closed for a long time unattended! This can lead to freezing of food and icing of the evaporator, since the control system is disabled.
Table of typical faults and solutions
To systematize the data obtained and simplify the diagnostic process, we suggest that you familiarize yourself with the summary table. It will help you quickly compare symptoms with probable causes and choose the correct algorithm of action.
| Symptom | Probable cause | Action | Complexity |
|---|---|---|---|
| The refrigerator does not turns on | Open circuit in the thermostat | Ring the contacts, replace the relay | Low |
| Continuous operation of the compressor | Contacts do not open | Check the cold response, replace | Low |
| Frequent on/off | Incorrect calibration or gas leak | Replacing the thermostat or finding a leak | Medium |
| Frost only at the evaporator | Shutdown too early | Differential adjustment or replacement | High |
| Clicks without starting the motor | Burning of relay contacts | Cleaning the contacts or replacing the unit | Low |
Analyzing the data from the table, you can see that most problems are solved by replacing the element. However, it is important to make sure that the problem is in the relay, and not in the compressor or refrigerant circulation system. A freon leak often gives similar symptoms (the compressor runs constantly), but replacing the relay in this case will not help.
If after replacing the thermostat the situation has not changed, it is worth checking the compressor start relay and the motor itself. Perhaps the problem lies deeper, and a professional diagnosis using a pressure manifold is required.
Replacing and setting up a new one thermostat
If the diagnostics confirm a malfunction, it is necessary to replace it. When purchasing a new item, pay attention to the labeling. Thermostats for different models of refrigerators (for example TAM-112, TAM-133, K-59) may differ in the length of the capillary tube and the temperature range of operation.
Installation is carried out in the reverse order of dismantling. Carefully insert the capillary tube into the evaporator socket, being careful not to damage it. Secure the thermostat housing and connect the wires strictly according to the previous photo or diagram. An error in the connection may result in a short circuit.
After assembling and turning on the refrigerator, adjustments may be required. In mechanical models, this is done experimentally: set the knob to the middle position and control the temperature in the chamber throughout the day. If necessary, adjust the position of the regulator.
In some cases, it is necessary to adjust the screws under the seal on the thermostat housing (range and differential screws). It is not recommended to do this without special equipment and knowledge, as you can reset the factory settings and the refrigerator will no longer support the desired mode.
⚠️ Attention: The technical characteristics of thermostats (on/off temperature) may vary even for models with the same markings from different manufacturers. Always check the parameters with the documentation or recommendations of the refrigerator manufacturer.
Where to buy an original thermostat?
It is best to look for spare parts using the full model code of the refrigerator or the article number of the old thermostat. Universal analogues may not work correctly, as they have a different temperature threshold.
Frequently asked questions (FAQ)
Is it possible to temporarily short-circuit the thermostat wires to keep the refrigerator working?
Yes, this is possible to temporarily preserve food. Shorting the wires removes the thermostat from the circuit and the compressor will run continuously. However, you will have to manually control the temperature and periodically turn off the refrigerator, otherwise everything will freeze, and the motor may burn out from overload.
Why does the new thermostat click, but the refrigerator does not turn on?
The click indicates that the relay mechanics are working. If the motor does not start, the problem may be with the compressor start relay, the motor itself, or the wiring to the new thermostat may be incorrect. Check for voltage at the compressor inlet.
How to understand that the thermostat is “lying” and shows the wrong temperature?
For this you need an external thermometer. Place it in a glass of water in the center of the chamber. If the thermometer readings differ greatly from the set temperature (for example, on the “3” regulator, and in the chamber +10°C or -5°C), it means that the calibration is broken.
Do you need to defrost the refrigerator before replacing the thermostat?
Yes, definitely. Ice in the chamber will make it difficult to access the evaporator and capillary tube mounting. In addition, working with electrical appliances in a damp environment is dangerous. Let the unit stand unplugged for at least 4-6 hours.
What is the difference between thermostats with one, two and three terminals?
The number of terminals depends on the functionality. Two terminals - simple opening of the compressor circuit. Three terminals - usually a contact is added to control a light bulb or fan. When replacing, it is important to follow the connection diagram, otherwise the light may not light up or the defrost may not work.