An unexpected stop of the compressor or, conversely, its continuous hum often signals a failure thermostat. This small but critical element controls the cycles of turning the motor on and off, maintaining the desired temperature in the chambers. If you notice that the food in the refrigerator has begun to deteriorate faster than usual or a crust of ice is forming, it may be time to replace the sensor.
Independent replacing the thermostat is a task quite feasible for a person who knows how to handle a screwdriver and understands the basics of electrical circuits. However, the risks associated with electrical current and refrigerants must be clearly understood before work begins. In this article, we will analyze an algorithm of actions that will help you safely dismantle the old regulator and install a new one.
It is worth noting that the design of refrigeration units from different manufacturers may differ significantly. Somewhere the thermostat is located inside the chamber, and somewhere it is hidden behind the rear panel from the outside. Understanding the principle of operation and strictly following the instructions will allow you to avoid common mistakes during installation.
The operating principle and design of the thermostat
Thermostat, or thermostat, is an electromechanical device that responds to changes in temperature in the evaporator or inside the chamber. The main working element is a bellows tube filled with a temperature-sensitive gas or liquid. When cooling, the pressure inside the tube drops, the contacts open, and the compressor stops.
When the temperature in the chamber rises, the gas expands, the pressure rises, and the contacts of the electrical circuit close. At this moment, compressorstarts, starting a new cooling cycle. The reliability of this mechanism depends on the quality of the contacts and the tightness of the bellows.
Modern models can be equipped with electronic sensors, but most household refrigerators, especially those released more than 10 years ago, use mechanical regulators. They are marked with various codes, for example TAM-133 or K-59, and require precise selection of an analogue when replacing.
⚠️ Attention: The thermostat bellows tube is made of thin metal. If handled carelessly, it can easily be damaged, which will lead to leakage of sensitive gas and complete inoperability of the new device. Be extremely careful when straightening the coils.
Understanding the physics of the process helps diagnose the problem. If the contacts are stuck closed, the refrigerator will freeze indefinitely. If they are oxidized and do not close, the engine will not start at all, despite the serviceability of the compressor itself and the start relay.
Diagnostics of a thermostat malfunction
Before disassembling the unit and buying spare parts, you need to make sure that the problem lies in the temperature controller. Often the symptoms can be similar to malfunctions of the start relay or the compressor itself. Primary diagnostics are carried out by visual inspection and listening to the operation of the unit.
The easiest way to check is to exclude the thermostat from the electrical circuit. To do this, you need to remove the terminals from the sensor contacts and connect them directly to each other using a jumper. If the compressor starts working after being connected to the network, it means that the circuit is working properly, and the regulator requires replacement.
- 🔍 Symptom 1: The compressor does not turn on, but when the thermostat contacts are closed, it starts working.
- ❄️ Symptom 2: The refrigerator freezes constantly, without turning off, a thick layer forms on the back wall ice.
- 🔌 Symptom 3: The regulator housing has visible damage, traces of melting or oxidation of the contacts.
For more accurate diagnostics, you can use a multimeter. In continuity mode, check the resistance between the contacts. At room temperature, the contacts should be closed (resistance close to zero). If you place the sensitive tube in the cold (for example, in a freezer), the contacts should open.
Why is it important to check with a multimeter?
It is impossible to visually determine the “sticking” of the contacts inside a sealed case. The test allows you to verify with 100% accuracy the integrity of the electrical circuit and eliminate false diagnostics.
If you find that the thermostat is faulty, do not rush to buy the first analogue you come across. The markings on the body of the old device are your main guide. Different models have different lengths of the capillary tube and temperature response range.
Necessary tools and preparation
To successfully replace the thermostat, you will need a minimum set of tools, which can be found in the garage of most home craftsmen. The main requirement is safety and cleanliness of work so as not to damage the insulation or internal elements of the refrigerator.
☑️ Tools for replacing the thermostat
First of all, you need to completely turn off the power to the refrigerator. Unplug the plug from the socket and make sure there is no voltage. This is a basic rule electrical safety, neglect of which can lead to serious injury or failure of electronics.
Prepare the workplace in advance. You will need good lighting, as many nodes are located in hard-to-reach places. If the refrigerator is built-in, it is advisable to pull it out or provide access to the back wall and top.
| Tool | Purpose | Importance |
|---|---|---|
| Screwdrivers (set) | Removing panels and fastening terminals | High |
| Multimeter | Checking circuit continuity | High |
| Pliers | Installing the tube and clamps | Average |
| Flashlight | Inspection of internal cavities | Average |
It is also recommended to have isopropyl alcohol or contact cleaner on hand to treat connections before installing a new one element. Clean contacts will ensure a reliable electrical connection and prevent sparking in the future.
Removing the old thermostat
The process of removing the old regulator depends on its location. In most models of refrigerators Indesit, Ariston and Stinol the thermostat is located inside the refrigerator compartment, in a plastic casing along with a lighting lamp. In models Atlant or Biryusa it can be located outside, above the doorway.
Consider the option with an internal location. First, remove the temperature control from the lever handle. Usually it is simply pulled together by hand or pryed off with a flat screwdriver if it has a fixing screw. Then unscrew the screws holding the plastic case.
Carefully remove the case out. You will see wires approaching it and a capillary tube going deep into the cabinet. Disconnect the electrical terminals after first remembering or photographing their location. The color marking of the wires may vary, so a photograph is the best way not to get confused.
⚠️ Attention: The capillary tube is secured with special clips or brackets on the evaporator. Don't pull it too hard! First, carefully release all attachment points, otherwise you may damage the evaporator or the tube itself.
After disconnecting the wires, you must remove the sensitive tube from the working area. It can be wound in a spiral around the evaporator. Unravel it slowly, being careful not to deform the coils. In some models, the tube passes through the door seal - in this case, act especially carefully so as not to break the seal of the chamber.
Installing and connecting a new thermostat
Installing a new element begins with preparing the sensitive tube. If the length of the tube of the new thermostat is longer than that of the old one, the excess is carefully rolled into a ring with a diameter of at least 3-4 cm. Sharp creases are unacceptable, as they will block the passage for gas.
Insert the tube into the same hole where the old one was located and secure it with standard clips on the evaporator. The contact of the tube with the surface of the evaporator must be tight; often for this, a special heat-conducting paste is used or simply pressed tightly with a metal plate.
The electrical connection is made strictly according to the diagram that you photographed earlier. If the markings on the new thermostat are different, use a multimeter to find the common pins. Typically, contacts are marked with numbers 3 and 4 (or L and C), and grounding is marked with the “ground” symbol.
Use reliable methods to connect wires. Twisting is a temporary solution. It is best to use soldering or special crimp terminals. If you use twisting, carefully insulate the connection with heat shrink or high-quality electrical tape to prevent short circuits.
- 🔧 Step 1: Fix the thermostat housing in the seat with screws.
- 🔌 Step 2: Connect the wires to the appropriate terminals, checking reliability contact.
- 🧊 Step 3: Install the temperature adjustment knob on the regulator shaft.
After installation is complete, assemble all decorative panels and lampshades in the reverse order. Make sure that no wires are pinched by plastic or touching moving parts or hot surfaces of the compressor.
Checking operation and setting
After assembly, you can proceed to testing. Plug in the refrigerator. In the first minutes you should hear a characteristic click and the compressor starts. If the motor is silent, try turning the thermostat knob to the maximum cold position - sometimes full spring force is required for the first start.
Let the unit run for 30-40 minutes. During this time, the temperature in the chamber should begin to decrease. Check whether the compressor switches off when the set parameters are reached. A normal operating cycle means that the refrigerator runs for about 10-20 minutes and rests for 20-30 minutes (depending on the load and ambient temperature).
If the refrigerator runs non-stop, it is possible that the sensitive tube is not pressed tightly enough to the evaporator or its length is incorrect. If the compressor does not turn on at all, double-check the contact diagram.
⚠️ Attention: Do not set the thermostat to the minimum temperature immediately after installation. Allow the system to return to normal for several hours. A sharp setting of the maximum can lead to freezing of the evaporator and false operation of the No Frost system.
The final adjustment is made using the adjusting screw, which is often hidden under a seal or located inside the handle rod. Turning clockwise usually increases the shutdown temperature (makes the cold less intense), counterclockwise - lowers it. Turn the screw in small steps (1/4 turn) and wait for the mode to stabilize.
Frequent installation errors
Even experienced craftsmen sometimes make mistakes that can negate all the work. One of the most common is ignoring the condition of the wire insulation. The old wiring may be dry, and when installing a new thermostat, it easily cracks, exposing the wires.
Another common mistake is incorrect positioning of the capillary tube. It should not be located near heat sources or in an area where it will not be washed by the flow of cold air from the evaporator. This will lead to incorrect operation of the entire cooling system.
Also, users often forget to check the grounding. If there is a ground terminal on the thermostat housing, it must be connected. This protects against electric shock in the event of a breakdown of the insulation on the refrigerator body.
- ❌ Error: Using ordinary electrical tape in the freezer (it becomes dull and peels off).
- ❌ Error: Tensing the capillary tube “in a string” (it should lie freely, without voltage).
- ❌ Error: Installing a thermostat with a different temperature range without reconfiguring the system.
Try to avoid these mistakes, and your refrigerator will last for many years. Remember that accuracy and attentiveness at the installation stage are more important than speed of work.
What to do if the new thermostat clicks, but the compressor does not start?
Check the compressor start relay. Often, if the thermostat is faulty, the relay operates in emergency mode and also fails. Replacing the thermostat will not solve the problem if the relay is burned out.
Is it possible to install a thermostat with a different marking?
Installing an analogue is possible, but only if the basic parameters match: temperature range, capillary tube length and type of contacts. Different manufacturers use their own codes, so it is better to select a replacement using correspondence tables (cross-reference). For example, thermostats Danfoss are often replaced with Kalto or Ortobal with similar characteristics.
Why does the refrigerator turn on immediately after being turned off?
This phenomenon is called a “short cycle”. Most often, the reason is that the thermostat differential is not set correctly or that the sensing tube is not in good contact with the evaporator. It is also possible that moisture gets on the regulator contacts, which causes a short circuit in the control circuit.
Is it necessary to defrost the refrigerator before replacing?
Yes, this is a mandatory requirement. Before starting work, the refrigerator must be completely defrosted and dried. Moisture inside the chambers can cause a short circuit when connecting electrical components, and ice on the evaporator will make it difficult to access the thermostat mounts.
How long does a new thermostat last?
The average service life of a high-quality mechanical thermostat is 5-7 years under normal use. Electronic sensors may last longer, but they are more sensitive to power surges. Regular cleaning of the condenser and the correct location of the refrigerator prolong the life of the entire unit.