Modern refrigerators Indesit with a No Frost system or static cooling often face the problem of evaporator freezing, which is directly related to the failure of the defrost system. If you notice that a thick layer of ice has formed on the back wall of the chamber, and the food has begun to deteriorate or, conversely, freeze, it is most likely that the defroster is faulty. This part is responsible for starting and stopping the heating of the heating element at the right moment, preventing the refrigerator from turning into an ice monolith. defrost sensor, which in everyday life is often called a defroster. This part is responsible for starting and stopping heating of the heating element at the right moment, preventing the refrigerator from turning into an ice monolith.
Diagnostics of this part does not require calling a specialist and expensive equipment, just basic knowledge of electrical engineering and the presence of a multimeter. Defroster malfunction is one of the most common reasons breakdowns in equipment of this brand, and its elimination often returns the unit to full operation in a matter of hours. In this article, we will analyze the algorithm of actions in detail so that you can independently determine the condition of the sensor.
Before starting any work, you must understand that Indesit refrigerator is a complex electrical device that requires compliance with safety measures. Checking the defroster is always carried out only on completely de-energized equipment, since working with live electrical circuits may result in electric shock or damage to the control board. It is also worth preparing the tool in advance so as not to interrupt the process halfway.
Symptoms of a malfunction of the defrost sensor
The first sign is that What defrost system does not work correctly is the appearance of a “fur coat” or ice crust on the back wall of the freezer or refrigerator compartment. When in good condition, ice should not accumulate as it melts regularly during defrost cycles. If you see that the evaporator is covered with a dense layer of ice, this is a direct signal that the heating element does not turn on or turns off too early.
In addition to visual signs, there are other symptoms that indicate a problem with defroster. The refrigerator may begin to work in increased mode, the compressor practically does not turn off, trying to compensate for the loss of cooling capacity due to the ice jam. An increase in temperature in the chambers may also be observed, even if the thermostat control is turned to maximum.
In some cases, a malfunction may be manifested by strange behavior of the electronics. For example, a refrigerator may periodically turn off for a long time or, conversely, the relay may frequently click. It is important to note that similar symptoms can occur when a heater or timer breaks down, therefore comprehensive diagnostics all circuit elements are required.
⚠️ Attention: If the refrigerator makes loud crackling sounds or you smell burnt wiring, immediately turn off the appliance from the network. Continued operation may lead to a fire or complete failure of the compressor.
Ignoring these signs often leads to more serious consequences, such as jamming of the compressor or damage to the plastic elements of the housing due to ice expansion. Timely check temperature sensor avoids costly repairs of the main components of the unit.
The design and operating principle of the No Frost system
To successfully carry out diagnostics, you need to understand exactly how it functions defrost cycle in refrigerators Indesit. The No Frost system is built on the circulation of cold air, which is cooled by passing through an evaporator hidden behind the rear panel. During operation, moisture inevitably condenses on the evaporator and freezes in the form of frost.
To remove this frost, a heating element (heating element) is used, which is turned on at the command of an electronic module or mechanical timer. The key element here is defroster (defrost sensor), which controls the temperature of the evaporator. While the temperature is low, the sensor is closed and allows current to pass to the heating element (or gives a command to turn on).
As soon as the ice melts and the temperature rises to a certain threshold (usually about +10...+15°C), defrost sensor opens the circuit, stopping heating. This prevents overheating of plastic parts and saves energy. If this mechanism is broken, the ice either does not melt at all, or the heating element heats in vain until the emergency thermostat turns it off.
It is important to distinguish between the types of sensors, since in different models Indesit they may differ. There are bimetallic sensors that work purely mechanically, and electronic (thermistors), the resistance of which varies depending on temperature. Testing principle They are similar, but there are nuances in the interpretation of multimeter readings.
What is the difference between a bimetallic sensor and a thermistor?
The bimetallic sensor is closed at low temperatures (resistance 0 Ohm), and opens when heated. The thermistor changes its resistance smoothly: usually at room temperature it is several kiloohms, and upon cooling it increases sharply. To accurately check the thermistor, a resistance table (RT table) is often required.
Preparation for diagnostics: tools and safety
Before you begin disassembly and measurements, it is necessary to ensure safe working conditions. Disconnection from the power supply is the first and most important rule. It is not enough to simply turn off the refrigerator with a button; if there is one, you need to remove the plug from the socket. This will protect you from electric shock and protect the electronic control board from power surges in the event of an accidental short circuit of the probes.
To carry out high-quality diagnostics, you will need a minimum set of tools. The main device will be multimeter (tester) capable of measuring resistance (Ohm) and ringing the circuit. You will also need screwdrivers (Phillips and flat head), you may need a hex wrench to remove panels in some models Indesit.
- 🛠️ Multimeter with working probes and battery.
- 🔧 Screwdriver set (Philips, flat, Torx).
- 🧤 Protective gloves (to avoid cutting yourself on ice or sharp metal edges).
- 🧊 Hair dryer or container with warm water (to speed up defrosting if ice interferes with access).
- 📸 Smartphone (to photograph the wiring diagram before disconnection).
Particular attention should be paid to access to the evaporator. In Indesit No Frost refrigerators, this often requires removing the back panel in the freezer compartment, and in some models, in the refrigerator compartment. Make sure you have enough space to work and good lighting.
☑️ Preparing for repairs
Access to the sensor: dismantling panels
Process of gaining access to defroster varies depending on the specific model Indesit. In most refrigerators with a No Frost system, the sensor is located directly on the evaporator, which is hidden behind the plastic back wall of the freezer. In models with a weeping system (static cooling), the sensor may be located in the area of the capillary tube or built into the housing.
Start by completely defrosting the refrigerator. Even if you plan to just test the sensor, the presence of ice on the evaporator can make it difficult to remove the panels and damage the fragile plastic if you move it carelessly. Leave the doors open for at least 12-24 hours until all the ice has completely melted.
After defrosting, remove any shelves, drawers, or runners that are blocking access to the back wall. Panel fastenings can be hidden under decorative plugs or located deep in the chamber. Be careful with plastic latches - the plastic in old refrigerators becomes brittle and breaks easily.
When the panel is removed, you will see an aluminum evaporator heat sink. Defrost sensor usually secured in a special hole in the evaporator fins or pressed against it with a metal bracket. Two wires come from it, which go to the connector or directly to the control board.
Checking the defroster with a multimeter: step-by-step instructions
The most reliable way to determine performance defrost sensor is to measure its electrical resistance. To do this, switch the multimeter to resistance measurement mode (Ohm) or continuity mode. If the sensor is bimetallic and is in a cold state (temperature below the response threshold), it must be closed.
Connect the multimeter probes to the sensor contacts. If the device shows resistance close to zero (0-5 Ohms) and emits a beep, then the circuit is closed. This is normal condition for a cold bimetallic sensor. If the multimeter shows one (infinity), then the sensor is broken and requires replacement.
To check the circuit opens, the sensor must be heated. This can be done by holding it in a warm palm or gently heating it with a hairdryer (without overheating!). When heated above the threshold temperature (usually +10...+15°C), the resistance should increase sharply to infinity, and the circuit should open. If this does not happen, the defroster is faulty.
In the case of electronic thermistors, the picture is different. Their resistance changes smoothly. At room temperature it is usually between 5 and 15 kOhm (the value depends on the model). As it cools, the resistance should increase. To accurately diagnose thermistors, it is better to have on hand technical documentation for a specific model Indesit.
| Sensor type | Condition (Temperature) | Normal reading | Failure sign |
|---|---|---|---|
| Bimetallic | Cold (< 5°C) | 0 - 5 Ohm (Short) | Infinity (Open) |
| Bimetallic | Warm (> 15°C) | Infinity (Open) | 0 Ohm (Stick) |
| Thermistor (NTC) | Room (~20°C) | 5 - 15 kOhm | 0 Ohm or Infinity |
| Thermistor (NTC) | Cooling | Growth resistance | Lack of response |
In addition to the sensor itself, be sure to check the integrity of the wires going to it. Often a break occurs not in the sensor itself, but at the point where the wire exits the housing or in the area of the connector. Ring each wire separately from the connector to the end.
Replacing and checking adjacent elements
If diagnostics showed that the defroster is faulty, it must be replaced. You need to buy a similar part with the same parameters (operation temperature, wire length, connector type). Installation is carried out in the reverse order: the sensor is inserted into the seat on the evaporator and fixed.
However, even if the sensor is working, the defrost system may not work due to other components. Be sure to check heating element (heating element). It must also ring (have a resistance, usually from 200 to 800 Ohms, depending on the power). If the heating element is broken, replacing the sensor will not solve the problem.
The third important element is the defrost fuse. It is installed in series with the heating element and burns out if overheated. If the fuse is blown, the circuit is broken and the heating element will not turn on, even if the sensor and the heating element itself are working. Its resistance should be zero.
⚠️ Attention: Never install a jumper in place of a blown defrost fuse. This can lead to the melting of the plastic parts of the refrigerator and a fire if the relay or sensor is stuck.
After replacing all faulty elements, reassemble the refrigerator without installing food yet. Turn it on and watch the first cycle of operation. Make sure that after a certain time (usually 6-12 hours) a characteristic clicking sound occurs and defrosting starts (if it is possible to track this using a timer or sound).
Frequently asked questions (FAQ)
Is it possible to operate a refrigerator with a faulty defroster?
Short-term operation is possible, but undesirable. Over time, the layer of ice on the evaporator will become so thick that it will block the air circulation channels. This will lead to overheating of the compressor, increased energy consumption and food spoilage. It is better not to delay repairs.
Where to buy an original defrost sensor for Indesit?
Original spare parts can be found in authorized service centers or specialized stores of spare parts for household appliances. When purchasing, pay attention to the markings (for example, KSD, DM05, etc.) and the temperature response threshold indicated on the part body.
Why does the ice not go away after replacing the sensor?
There may be several reasons: the defrost heating element itself is faulty, the fuse is blown, there is a problem with the timer or control module, or it is broken chamber tightness (excess moisture enters the system). It is also possible that the new sensor is installed incorrectly or has incorrect parameters.
How much does it cost to replace a defroster in the service?
The cost consists of the price of the spare part and the work of the technician. On average, taking into account the on-site visit, diagnostics and replacement can cost from 2,000 to 4,000 rubles, depending on the region and the difficulty of accessing the evaporator in your model Indesit.