Failure of the temperature control system is one of the most common reasons for calling service, although in many cases you can fix the problem yourself. Thermostat TAM 133 is a mechanical regulator that is responsible for turning the compressor on and off depending on the temperature in the evaporator. If your refrigerator stops turning off, freezes too much, or, conversely, stops cooling, the problem often lies in this unit. Understanding the operating principle and connection diagram will help you not only replace the part, but also correctly set the operating mode of the unit.
Before starting disassembly, it is important to make sure that the malfunction is really related to the thermostat, and not to a freon leak or compressor failure. Mechanical thermostats series TAM from the manufacturer Danfoss (or their analogues) are reliable, but over time their contacts can burn out and the bellows tube of the temperature-sensitive element lose its tightness. It is critically important to completely de-energize the refrigerator before starting work by removing the plug from the socket, since you will be working with 220 volt elements. Ignoring this rule can lead to electric shock or a short short circuit.
⚠️ Attention: Mechanical thermostats cannot be repaired. If the diagnostics showed their malfunction, the only solution is a complete replacement with a new, similar device with identical characteristics and the length of the capillary tube.
Diagnostics and signs of a thermostat malfunction
Symptoms of a thermostat failure can be varied, and they do not always indicate it with a 100% guarantee. Most often, owners are faced with a situation where the compressor runs continuously without turning off for hours. In this case, a “snow coat” forms in the refrigerator compartment, the food freezes, and the unit itself becomes very hot on the sides. This indicates that thermostat contacts they are stuck in the closed position and do not open the circuit when the set temperature is reached.
The opposite situation - the refrigerator does not turn on at all. The light inside is on, a humming or clicking noise is heard, but the engine does not start. Here the reason may lie in an open circuit inside the regulator or in the fact that the temperature-sensitive element has stopped responding to heat. It is also worth paying attention to the adjustment knob: if it scrolls freely, without characteristic clicks, or, conversely, is jammed, this is a sure sign of internal failure of the mechanism TAM 133.
Sometimes a symptom such as a short operating cycle occurs: the compressor turns on for 2-3 minutes, then turns off for the same time. This may indicate that capillary tube the thermostat has lost sensitivity or is not properly secured to the evaporator. In some models of refrigerators, especially old Soviet or early imported ones, the thermostat can “lie” by 5-10 degrees, which requires not replacement, but proper calibration of the adjusting screw.
Preparation for replacement and necessary tools
To successfully replace the thermostat, you will need a minimum set of tools, which most people have in their garage men. The main focus should be on safety and neatness, as the plastic parts in older refrigerators can be fragile. You will need screwdrivers (Phillips and flat-head), side cutters or wire strippers, and a multimeter for initial testing of the circuit. Don't forget to prepare electrical tape or heat shrink to insulate the connections.
Before removing the old thermostat, you need to gain access to its installation location. In single-compartment refrigerators, the thermostat is usually located inside the refrigerator compartment, under the lampshade or in a special plastic case on the wall. In dual-compartment models with a single compressor, it is often located at the top of the refrigerator compartment. You will have to remove the protective covers, the adjustment knob and, possibly, dismantle the lampshade to get to the mounting unit.
Pay special attention to the markings of the new part. Thermostats of the series TAM 133 have various modifications, differing in the temperature range of operation and the length of the capillary tube. If you set the thermostat to the wrong range, the refrigerator will either run too long or fail to reach the desired temperature. The length of the tube is also important: if it is too short, you will not be able to properly attach the sensing element to the evaporator.
Connection diagram and analysis of contacts
The most important step is the correct connection of the wires to the new thermostat. Thermostats TAM 133 usually have three or four contacts, depending on the modification and the presence of the lamp ignition function. Standard contact markings include numbers 3, 4, 6 and sometimes 3.3 or L. Understanding the purpose of each pin is necessary for the correct operation of the refrigerator and lighting system.
Contact 3 (or 3.3) is usually the phase input from the mains or from the defrost button. Contact 4 is an output to the compressor, which closes when the temperature drops. The contact 6 is often responsible for the refrigeration chamber lighting lamp circuit. If your thermostat model has four contacts, then the second contact 3 (sometimes designated as 3L) serves to supply power to the lamp. An incorrect connection can lead to the fact that the light in the chamber will not light up or the compressor will not start.
The table below shows a typical pinout for the most common modifications of thermostats used in refrigerators "Atlant", "Biryusa", "Indesit" and others:
| Contact on the thermostat | Purpose | Where it is connected | Wire color (approximate) |
|---|---|---|---|
| 3 (or 3.3) | Phase input (L) | From the defrost button or network | Red / Brown |
| 4 | Output to compressor | Engine start relay | Black / Orange |
| 6 | Light lamp | Lamp socket in the chamber | White / Yellow |
| 3.3 (L) | Duplicate input/output | Depends on the refrigerator circuit | Green / Blue |
When connecting, it is important to observe polarity, although this is not always critical for mechanical contacts, it is better to follow the color coding of the old thermostat wires. If the wire colors do not match the factory ones (which often happens after previous repairs), use a multimeter in test mode. Find the wire coming from the defrost button and the wire going to the compressor relay. Switching should occur between these circuits.
⚠️ Attention: Make sure that the wires are tightly seated in the thermostat terminals. Poor contact will lead to sparking, heating and eventual melting of the plastic, which can cause a fire.
The process of installing and fastening the capillary tube
After the electrical connection, it is the turn of the mechanical installation. The thermostat capillary tube is a thin copper conductor that contains refrigerant inside. It must be pressed firmly against the surface of the evaporator to accurately read the temperature. Depending on the design of your refrigerator, the tube can be inserted into a special hole in the chamber wall or attached directly to the evaporator fins.
For fastening, a special clamping bar is used, which is secured with a screw. It is important not to overdo it when tightening the screw: too much pressure can deform or even bite the thin tube, which will lead to failure of the new thermostat. The tube should lie flat, without kinks or creases. The minimum bending radius is usually 30 mm, so avoid sharp bends during installation.
☑️ Thermostat installation checklist
If the length of the capillary tube of the new thermostat is longer than that of the old one, the excess can be carefully twisted into a ring with a diameter of at least 4-5 cm and placed in the free space behind the back wall of the refrigerator compartment or in a niche. The main thing is that the tube does not touch moving parts, vibrating elements of the compressor or sharp metal edges, which can damage it over time.
What to do if the tube is too short?
If you bought a thermostat with a shorter capillary tube, you can carefully extend it. To do this, use a copper tube of suitable diameter and soldering with silver-containing solder. However, this requires skills and tools. It is easier and more reliable to select a thermostat with a tube length equal to or greater than the original, and carefully place the excess.
Adjusting and setting the temperature mode
After installing the new thermostat and assembling the refrigerator, it is necessary to carry out its initial adjustment. Mechanical regulators have a calibration screw, which is often accessed through a hole in the adjustment knob or through a special hole in the housing. Turning this screw allows you to shift the temperature range of the contacts.
To set it up, you will need a thermometer that can be placed in a glass of water and placed in the center of the refrigerator compartment. Turn on the refrigerator and let it run for a few hours. If the temperature in the chamber does not correspond to the set value on the knob (for example, the knob is at “3”, and in the chamber it is +10°C or -2°C), an adjustment must be made. Turning the screw clockwise usually increases the shutdown temperature (the refrigerator will freeze weaker), and counterclockwise - decreases it (the unit will freeze more strongly).
After each turn of the screw by 1/4 or 1/2 turn, you need to wait 30-60 minutes for the temperature to stabilize. Setting accuracy depends on many factors: load cameras, room temperature, condition of door seals. Do not expect instant results, give the system time to react to changes.
Typical errors during installation and troubleshooting
Even experienced technicians sometimes make mistakes that can ruin all repair efforts. One of the most common mistakes is incorrect positioning of the capillary tube. If it does not fit tightly to the evaporator or is secured to the “warm” zone, the thermostat will give incorrect readings. As a result, the compressor may operate with short cycles or, conversely, overload.
Another common problem is ignoring the condition of the wires. If the insulation on the wires going to the thermostat is cracked or melted, they need to be cleaned and rebuilt using high-quality solder and heat shrink. Twists at the joints are unacceptable, as they create transition resistance, which leads to heating. It is also worth checking the condition of the terminals on the thermostat itself: they should be clean and not oxidized.
If after replacing the thermostat the refrigerator started working, but after a while it stopped turning off again, check the pressure in the system. Sometimes the reason is not the thermostat, but a freon leak or a clogged capillary system of the refrigeration unit. In such cases, replacing the thermostat gives only a temporary effect or does not solve the problem at all. In this case, a more in-depth diagnosis will be required with the participation of a specialist and a pressure manifold.
⚠️ Attention: The characteristics of thermostats and connection diagrams may vary slightly depending on the manufacturer of the refrigerator and the year of manufacture of the model. Always check the technical documentation of the specific device.
Questions and answers (FAQ)
Is it possible to install a TAM 133 thermostat instead of TAM 125 or TAM 112?
Technically this is possible, since the mounting locations and electrical parameters are similar. However, these thermostats have different temperature response ranges. TAM 133 is designed for single-chamber refrigerators or double-chamber refrigerators. Installing the wrong model may result in incorrect operation: either the food will defrost or freeze. It is better to look for a complete analogue by catalog number.
Why does the thermostat spark when switching?
Sparking indicates the passage of an electric arc between the contacts at the moment of their opening or closing under load. This may be caused by burnt contacts, a weak mechanism spring, or excessive current load (for example, if the compressor start relay is faulty and draws too much current). If the sparking is strong and accompanied by a crackling sound, the thermostat needs to be replaced.
How to check the thermostat with a multimeter without removing it?
To check, remove the lampshade or get to the contacts. Unplug the refrigerator. Remove the wires from the thermostat contacts (after photographing the circuit). Turn the multimeter into dialing mode. Connect the probes to the input and output contacts of the compressor. At room temperature the circuit should ring (be closed). If you put the sensitive tube in the freezer (or heat it in your hands, depending on the type), the contacts should open and stop ringing.
What do the numbers on the thermostat knob mean?
The numbers on the knob (usually from 1 to 7 or from Min to Max) do not indicate degrees Celsius. These are symbols for cooling power. “1” is minimum cooling (the compressor turns off at a higher temperature), “7” or “Max” is maximum cooling (the compressor works longer, bringing the temperature to lower values). The optimal mode for constant operation is considered to be position “3” or “4”.