Modern refrigerators Samsung with system No Frost are complex units where each element is responsible for a stable temperature regime. One of the key components to ensure trouble-free operation is the defrost sensor. It is this small device that informs the electronic control module about the temperature of the evaporator, starting or stopping the defrosting process.
If the sensor fails, the refrigerator stops defrosting the evaporator correctly, which leads to it becoming overgrown with ice and stopping cooling in the main chamber. You may notice that the refrigerator is hummingit is not getting cold, or a snow coat is forming on the back wall. In this article, we will analyze in detail how to independently diagnose this element using a conventional multimeter.
To successfully perform the test, you do not need complex professional equipment, just basic knowledge of electrical engineering and a set of tools. We will consider not only the dialing process itself, but also indirect signs of a malfunction that will help you save time on disassembling equipment.
Principle of operation and symptoms of malfunction
A defrost sensor, or thermistor, is a resistor whose resistance varies depending on the ambient temperature. In refrigerators Samsung it is usually mounted directly on the evaporator or in close proximity to it. When the temperature drops to a certain threshold (usually about -7...-10°C), the sensor sends a signal to the control module about the need to turn on the defrosting heating element.
If thermistor transmits incorrect data or breaks the circuit, the control system “thinks” that defrosting is not required, or, conversely, cannot start the heater. This leads to the evaporator becoming overgrown with ice, the fan stops moving air, and the refrigerator compartment becomes warm. Often the first signal is the appearance of an error code on the display, for example 22C or 24C, which indicate problems with the sensors.
⚠️ Attention: Do not confuse the defrost sensor with the air temperature sensor in the chamber. The first hangs on the evaporator (behind the back wall), the second is usually located inside the refrigerator or freezer.
It is difficult to visually determine the breakdown, since the thermistor looks like a sealed capsule with wires. However, if you notice that the defrost cycle does not start at all, or, conversely, the refrigerator defrosts too often, you should suspect this particular element. Also, a malfunction may be indicated by constant operation of the compressor without stopping.
A frequent cause of failure is not so much a breakdown of the element itself, but a break in the wires or oxidation of the contacts in the connector. Therefore, before replacing, it is always worth checking the integrity of the wiring going to the evaporator.
Necessary tools and preparation for diagnostics
Before you start disassembling the refrigerator Samsung, you need to prepare the workplace and tools. You will need a Phillips screwdriver to remove the panels, a knife to carefully remove the ice (if it is in the way) and, most importantly, a multimeter. Without a measuring device, the test will only be of a guessing nature and will not give an accurate result.
The multimeter must be able to measure resistance in the range from 0 to 20 kOhm. Before starting work, be sure to disconnect the refrigerator from the power supply. Working with electrical appliances under voltage is dangerous to life, and in addition, you can damage the electronic control module if there is an accidental short circuit.
☑️ Preparing to check the sensor
To access the sensor in most Samsung models, you will need to remove the back panel in the freezer. In some cases, if there is too much ice, you will have to first defrost the unit for 24 hours to prevent water from damaging the electronic components when removing the panels.
Have a water container and a rag on hand, as condensation or residual water from the drain may leak from the evaporator when removing the panel. Carefully disconnect all connectors without pulling the wires, as the plastic becomes brittle in the cold.
Dismantling and visual inspection of the element
After removing the back panel of the freezer, you will have a view of the evaporator. The defrost sensor is usually fixed in a special hole on the evaporator tubes or pressed against them with a metal bracket. In models Samsung with the system Twins Cooling access may be a little more difficult due to the additional partition.
Visually inspect the sensor housing. There should be no cracks, traces of burning or melting on it. The wires coming from it must be intact, without signs of rodent bites or mechanical damage to the insulation. If you see obvious damage to the insulation, the problem may lie in a short circuit in the wiring, and not in the thermistor itself.
⚠️ Attention: When removing the sensor, do not use excessive force. The plastic body of the thermistor is fragile and can easily be chipped, rendering further testing pointless.
Disconnect the sensor connector from the wiring harness. On some models, the connector may be filled with ice or covered with frost. Gently dry it with a hairdryer on a cold setting or let it thaw naturally. An attempt to disconnect a frozen connector by force will lead to breakage of the contacts.
Where exactly is the sensor located?
In most Samsung refrigerators, the defrost sensor is located on the left or right side of the evaporator, closer to the heating element. It can be fixed in an aluminum sleeve or simply inserted into the hole between the radiator fins.
Checking with a multimeter: step-by-step instructions
The most reliable way to check thermistor is to measure its resistance. Switch the multimeter to resistance (Ohm) measurement mode, selecting a limit of 20 kOhm. Connect the probes of the device to the contacts of the sensor connector. The polarity in this case does not matter, since it is a resistor.
The readings of the device will depend on the current temperature of the sensor. If the sensor has just been removed from the freezer, its temperature will be low and the resistance will be high. If it has been out of the refrigerator for several hours, the resistance will drop. For accurate diagnosis, you need to know the temperature of the element at the time of measurement.
Below is a table of typical resistance values for refrigerator defrost sensors Samsung. Please note that the values may vary slightly depending on the specific model and year of manufacture.
| Temperature (°C) | Resistance (kOhm) | Acceptable error | Status |
|---|---|---|---|
| -10°C | 25 - 30 kOhm | ±10% | Normal (frozen) |
| 0°C | 15 - 16 kOhm | ±10% | Normal (ice boundary) |
| +25°C | 5 - 6 kOhm | ±10% | Normal (room temp.) |
| Infinity | ∞ (Open) | - | Faulty |
| 0 Ohm | 0 (Short circuit) | - | Faulty |
If the multimeter shows one at the 20 kOhm limit (infinity) or zero, the sensor is faulty and requires replacement. Also a sign of a malfunction is a strong deviation from the table values. For example, if at room temperature the device shows 20 kOhm instead of 5 kOhm, the control module will receive incorrect temperature data.
For a more accurate test, you can place the sensor in a glass of water of a known temperature and measure the resistance over time. This will make sure that the resistance changes smoothly, without jumps, which indicate an internal defect in the crystal.
Analysis of error codes on the display
Refrigerators Samsung are equipped with a self-diagnosis system that displays error codes on the display. To enter the diagnostic mode, you often need to simultaneously press the buttons Freezer and Fridge (or Power Cool and Power Freeze) for a few seconds. Symbols may appear on the screen indicating a specific malfunction.
Error codes associated with the defrost sensor usually begin with the number 2. For example, 21C, 22C, 23C, 24C. Each number corresponds to a specific sensor. The decoding of the codes can be found in the instructions or service manual for your specific model. If the corresponding code is lit on the display, in 90% of cases this confirms the need to replace the element.
However, do not blindly rely only on the codes. The electronic module may generate an error if the sensor circuit is simply open due to poor contact in the connector, but the thermistor itself is working. Therefore, visual checking and testing with a multimeter remain mandatory steps.
Sometimes resetting the error (Reset) helps to temporarily clear the indication, but if the physical fault is not resolved, the code will appear again after the next defrost cycle. Constantly ignoring the error can lead to compressor failure due to overload.
Replacing the sensor and assembling the refrigerator
If the check confirms the malfunction, you need to purchase a new one thermistor. Original spare parts Samsung have special markings, for example DA32-10105N or similar. The use of universal sensors with similar resistance is possible, but requires precise selection, since the resistance curve may differ.
Installation of a new sensor is carried out in the reverse order. Carefully insert the sensing element into the hole on the evaporator until it stops. It is important to ensure tight contact of the sensor body with the surface of the evaporator for correct temperature reading. Some technicians recommend using thermal paste to improve heat transfer, although it is rarely used regularly.
⚠️ Attention: Do not bend the sensor wires at an acute angle close to the body. This can lead to fracture of the cores inside the insulation when the compressor vibrates.
Connect the connector, making sure that the latch clicks. Reinstall the freezer back panel and secure with screws. Plug in the refrigerator. The initial defrosting cycle may take some time, so do not expect instant cooling.
Frequently asked questions and problems during diagnostics
In the process of self-repair, refrigerator owners Samsung often faced with nuances that are not described in the instructions. For example, many people do not know that the sensors in the refrigerator and freezer compartments may have different resistances, despite their external similarities. By mixing them up, you will get incorrect operation of the unit.
Also a common mistake is checking the sensor “on weight”, without taking into account its real temperature. Multimeter readings at +25°C and at -15°C will be radically different. Always evaluate the measurement result in the context of the current temperature of the element.
If after replacing the sensor the problem does not disappear, it is worth checking the integrity of the defrosting heating element and the serviceability of the fuse (defroster). Often these elements fail simultaneously or sequentially, forming a chain of malfunctions in the defrost system.
Is it possible to temporarily short-circuit the sensor?
Theoretically it is possible, but this will cause the refrigerator to think that the temperature is always low and will not start defrosting. This will cause ice accumulation in 1-2 days.
Which sensor most often fails in Samsung No Frost?
The freezer evaporator defrost sensor most often breaks down, as it is subjected to constant heating and cooling cycles, as well as exposure to moisture. Air sensors in the chambers last longer.
Is it possible to drive with a faulty defrost sensor?
Long-term operation of a refrigerator with a faulty defrost sensor will lead to the formation of an ice block on the evaporator. This will block air circulation, increase the load on the compressor and can lead to expensive repairs.
Where to buy an original sensor for Samsung?
It is better to buy original spare parts at authorized service centers or specialized spare parts stores for household appliances. There are many cheap analogs on the market that may have an error in resistance.
Why does the multimeter show different values?
The resistance of the thermistor directly depends on temperature. If you hold the sensor in your hand, it heats up and the readings “float”. For an accurate measurement, place it on the table and let it lie for 5-10 minutes.