The situation when food in the refrigerator compartment begins to freeze or, conversely, deteriorates due to insufficient cold, often indicates a failure of the control electronics or sensors. In older models and many modern units, the key element of the control system is thermostat (thermostat), which opens and closes the electrical circuit of the compressor depending on the temperature inside the chamber. Replacing this element yourself requires care, but it is quite within the power of a home craftsman if you strictly follow safety precautions and the sequence of actions.
Before you start disassembling, you need to make sure that the problem lies in this particular unit. If the refrigerator hums continuously and does not turn off, or the compressor does not start at all when the start relay is working, it is likely that intervention in the thermostatic system will be required. It is important to understand that mechanical thermostat is a sealed device that cannot be repaired and requires complete replacement if a malfunction is detected.
⚠️ Attention: Before starting any work on dismantling electrical equipment, be sure to disconnect the refrigerator from the electrical network. Working with live wiring is deadly, and residual current can damage the sensitive electronics of modern inverter models.
The replacement process varies depending on the design of the refrigeration unit, the location of the sensor and the type of control (mechanical or electronic). In this article, we will analyze the universal principles applicable to most household models, and will pay special attention to the nuances of setting, which are often overlooked, which leads to repeated breakdowns.
Diagnostics of the fault and selection of components
Installing a new temperature controller does not make sense if competent diagnostics have not been carried out. Symptoms may be similar to refrigerant or compressor problems, so it is important to rule out other possibilities. The main sign of a thermostat malfunction is the incorrect operation of the compressor: it either works without stopping, trying to achieve a non-existent “ideal” cold, or is silent, despite the fact that the chamber is already warm.
To accurately determine the type of element required, you need to remove the old thermostat and study the markings on its body. Manufacturers use various codes, such as TAM, K59, DF etc., which indicate the operating temperature range and the length of the capillary tube. Incorrect selection of an analogue will lead to the fact that the refrigerator will operate in abnormal mode, quickly wearing out the motor resource.
When choosing a spare part, pay attention to the following parameters:
- 🌡️ Temperature range: must meet the requirements of your climate zone and type of chamber (main or freezer).
- 📏 Length of the capillary tube: critical parameter; if the tube is too short, you will not be able to position the sensor correctly, and if it is too long, you will have to carefully lay it out.
- 🔌 Contact configuration: the number of terminals and their location must match the original, so as not to redo the wiring harness.
You should not buy the cheapest analogues of unknown brands, since their calibration accuracy often leaves much to be desired. It is better to give preference to original spare parts or proven analogues from well-known manufacturers, such as Danfoss or Orbital.
Preparation of tools and workplace
High-quality installation of a thermostat is impossible without proper preparation. You will need not only a standard set of screwdrivers, but also specialized tools for working with electrical and refrigerant (in the case of mechanical systems). The workplace should be well lit, since the internal structure of the refrigerator is often hidden in hard-to-reach niches.
To successfully complete the task, prepare the following tools:
- 🔧 A set of screwdrivers (phillips and flathead of different sizes) for removing panels and fasteners.
- 🔌 A multimeter or tester to check the integrity of the circuit and contacts.
- 🧤 Dielectric gloves to protect against accidental electric shock.
- 🔦 A powerful flashlight, since the lighting inside the refrigerator is often not enough for delicate work.
Pay special attention to the cleanliness of the work area. Dust and dirt trapped inside the electrical unit or on the contacts of a new thermostat can cause short circuits or oxidation of the contacts in the future. It is recommended to wipe all surfaces in advance and prepare a container for folding the screws so as not to lose them during disassembly.
⚠️ Attention: If you find traces of oil or a greenish coating on the tube of the old thermostat, this may indicate a freon leak where the tube enters the housing (if the thermostat is built-in). In this case, simply replacing the thermostat will not help - you need to call a technician to charge the system.
☑️ Preparing to replace the thermostat
Removing the old thermostat
The process of removing the faulty element depends on its location. In most models of mechanically controlled refrigerators, the thermostat is located inside the refrigerator compartment, often hidden behind a plastic lampshade or decorative trim on the top wall. In some designs, it is accessed through the rear panel outside the unit.
The dismantling procedure usually looks like this:
- Carefully remove the plastic cover or shade that hides the thermostat. They are often held in place by clips that require careful handling to avoid breaking the plastic.
- Disconnect the temperature control knob. It can simply be removed by hand or be fixed with a locking screw that needs to be unscrewed.
- Unscrew the mounting screws holding the thermostat housing.
- Take a photo of the location of the wires before disconnecting them. This is a critical step as wire colors may vary between models.
After disconnecting the wires, you must remove the sensing capillary tube from the evaporator. It can be fixed in a special hole or pressed with a bar. Act slowly, without sudden jerks, so as not to damage the tube and not to break the tightness of the system if it passes through the chamber wall.
If access is from the outside, through the back cover, then after removing the metal panel you will see a black box with wires coming out. The principle of operation is similar: fix the position of the wires, unscrew the fasteners and carefully remove the sensor. In models with a system No Frost the thermostat is often located in the cold air supply channel.
What to do if the wires are mixed up?
If you forgot to take a photo of the circuit, use a multimeter in testing mode. Close the contacts on the thermostat (or heat it in your hands) and look for a pair that “rings.” This is the compressor control circuit. The third wire (if any) usually goes to a light bulb or fan.
Connection diagram and installation of a new element
Installation of a new thermostat is carried out in the reverse order of dismantling. The main rule is exact matching of the color markings of the wires. However, if you use a generic equivalent, the colors may not match. In this case, you need to rely on the diagram provided by the manufacturer of the new element, or use a multimeter to check the circuits.
Typical connection diagram for a mechanical thermostat with three contacts:
- ⚡ Pin 1 and 2: main compressor on/off circuit (often closed when the temperature drops).
- 💡 Contact 3: signal light circuit (opens when the compressor is running and closes when it is turned off).
- ❄️ Grounding: if provided by the housing design.
When installing, make sure that the wires are securely fixed in the terminals and do not dangle. Vibration from a running compressor can eventually loosen a poor connection, causing sparking and heating. Carefully insert the capillary tube of the new sensor into the evaporator hole to the same depth to which the old one was immersed. Secure the tube with standard fasteners or sealant, if necessary for tightness.
| Type of contacts | Function | Cold condition | Warm condition |
|---|---|---|---|
| Normally closed | Compressor power supply | Open (stop) | Closed (start) |
| Normally open | Signal lamp | Closed (lit) | Open (not lit) |
| Grounding | Safety | Constantly | Constantly |
⚠️ Attention: Never simply twist the wires or insulate them with electrical tape without using terminal blocks. In conditions of high humidity inside the refrigerator, the twists quickly oxidize, which leads to an increase in resistance and a fire hazard.
Calibration and adjustment of the temperature regime
After the physical installation and connection of the electrical part, the adjustment stage begins. Mechanical thermostats often require calibration, as the factory settings may not correspond to actual operating conditions or the characteristics of your specific refrigerator. The adjustment is carried out through a special screw located on the thermostat housing.
This screw is usually hidden under a seal or plug and is marked with notches or letters. Turning the screw changes the contact opening temperature. However, without special equipment (probe thermometer) it is difficult to accurately set the degrees. Therefore, it is recommended to proceed by trial and error, monitoring the temperature in the chamber using an external thermometer installed in a glass of water.
If your refrigerator is equipped with electronic controls, the process of “installing” the thermostat (temperature sensor) often ends with entering the service menu to reset errors. In such models, the sensor is a thermistor whose resistance changes with temperature. Replacement is carried out in the same way, but after switching on, a self-diagnosis cycle may be required.
Key adjustment points:
- 🔩 Adjustment screw: turn it no more than half a turn at a time, waiting several hours for the mode to stabilize.
- 🌡️ Differential: the difference between the switch-on temperature and turning off the compressor. In mechanics it is fixed, in electronics it is adjusted by software.
- ⏳ Waiting time: after the first adjustment, let the refrigerator run a full cycle (turn on and off on its own) before adjusting again.
Checking functionality and common errors
The final stage is testing the assembled system. Plug in the refrigerator and set the regulator to the middle position. Normally, after a few minutes (or immediately if the chamber is warm), the compressor should start. Follow the first cycle of operation: the refrigerator should reach the temperature and turn off.
The most common mistakes made during self-installation:
- Incorrect seating depth tubes: if the sensitive element does not reach the cooling zone or, conversely, touches the evaporator wall directly, the temperature readings will be incorrect.
- Poor contact: loose screws in the terminals lead to heating and burning of the contacts, which will damage the new thermostat in a short time.
- Ignoring tightness: the hole through which the capillary tube passes must be carefully sealed, otherwise warm humid air will get inside, causing freezing and malfunction.
If after replacing the thermostat the refrigerator does not work correctly (for example, it turns on too often), check the door seal and the absence of drafts. Sometimes the problem is not in the new part, but in the operating conditions. You should also make sure that you have not mixed up the wires going to the fan (in systems No Frost) and the compressor.
⚠️ Attention: If after replacing the thermostat the compressor hums but does not start, or the machine in the panel immediately knocks out, immediately turn off the device. Probably, the problem is not in the thermostat, but in the starting relay or motor windings, and further switching on can permanently damage the motor.
A correctly installed and configured thermostat prolongs the life of the compressor and ensures the safety of products. Do not be afraid to refer to the instructions of specific models, as design features may make adjustments to the general algorithm of actions.
Is it possible to install a thermostat from another refrigerator model?
Yes, you can, if the fit dimensions, capillary tube length and temperature range match. However, it is better to look for the original spare part number or a complete analogue recommended by the manufacturer to avoid problems with calibration.
Why does the refrigerator not turn off after replacing the thermostat?
Possible reasons: the calibration washer is incorrectly set, the thermostat is set to too low a temperature, the new sensor itself is faulty, or the problem lies in a freon leak, which is why the desired temperature is not physically achieved.
Do you need to defrost the refrigerator before replacing the thermostat?
Complete defrosting is not necessary if you work quickly and carefully. However, if access is required through the rear panel or there is a risk of moisture getting on the contacts, it is better to first defrost the unit and wipe it dry.
How to understand that the thermostat is set correctly?
Ideal setting: the compressor operates cyclically (for example, it works for 10-15 minutes, rests for 20-25), in the main chamber the temperature is kept within +2...+6°C, and the food in the freezer is solid. Products do not freeze or spoil.