Sudden fouling of the evaporator with a “coat” of ice often indicates a failure of the No Frost system. One of the main reasons for such a breakdown is a burnt-out heating element, which is often called defrosterin technical documentation. If the refrigerator has stopped freezing or an ice monolith has formed on the back wall of the freezer, the first step is to eliminate the malfunction of this particular unit.
Checking the defroster with a multimeter is a basic procedure that is accessible even to a beginner in repairing household appliances. You don't need sophisticated equipment, just a standard digital tester and a minimal set of tools to disassemble the case. Understanding the principle of operation Defrosting heating element will allow you to quickly determine whether a part needs to be replaced or the problem lies in the timer and sensors.
In this article we will analyze the fault finding algorithm in detail. We will look at how to correctly get to the heater, which values on the multimeter screen are considered normal, and which indicate an open circuit. Competent diagnostics will save you time and money, allowing you to avoid buying unnecessary spare parts.
Principle of operation and signs of malfunction of the heating element
The No Frost system is designed so that moisture does not turn into ice on the evaporator, and evaporated. Responsible for this process is defrost cycle, which starts automatically at certain intervals. The key element here is a tubular electric heater, or defroster, which heats up and melts the ice. If it stops working, ice accumulates, blocking the circulation of cold air.
You can determine a breakdown not only by the ice inside the chamber. There are obvious symptoms that should alert the owner of the equipment even before disassembly begins. Often, users ignore them, believing that the refrigerator is simply “tired,” although the problem is solved by replacing one part.
- 🧊 A thick layer of ice or snow is visible on the back wall of the freezer, although there was none before.
- ❄️ The refrigerator is humming louder than usual, as the compressor is working non-stop, trying to compensate for the bad air circulation.
- 🌡️ The temperature in the main chamber has increased, the food has begun to deteriorate faster, although the regulator is at maximum.
- 💧 Water appears under or inside the refrigerator, which does not have time to evaporate or go into the drainage due to the ice plug.
Important understand that these symptoms may indicate other problems, for example, a malfunction defrost sensor or the timer. However, it is the heating element that burns out most often due to the natural wear of the nichrome spiral. If the heating element is intact, but does not heat, it means that the circuit is broken somewhere else.
Preparation for diagnostics and safety measures
Before picking up a multimeter, it is necessary to ensure complete safety of the work. Electric current and water are a dangerous combination, so you absolutely cannot ignore electrical safety rules. Any diagnostics begins with disconnecting the device from the network.
⚠️ Attention: Before starting any work on disassembling the refrigerator, be sure to disconnect it from the power supply! Remove the plug from the outlet. Working with a multimeter under voltage requires high qualifications and special permission.
You will need a standard set of tools: screwdrivers (Phillips and flat), possibly a knife or spatula to carefully remove the ice if the chamber is completely frozen. Also prepare a container to drain the water that forms when the ice melts during defrosting.
To check the resistance you will need multimeter. Any model will do, even the most budget one. The main thing is that it has a resistance measurement mode (indicated by the symbol Ω - Omega). Before starting measurements, make sure that the probes are working properly and that the battery in the tester is not dead.
If there is a lot of ice inside the freezer, let the refrigerator completely defrost. This may take from 10 to 24 hours. An attempt to chip the ice with a knife can damage the evaporator or the heating element itself, which will make repairs impossible.
☑️ Ready for testing
Access to the heating element
The location of the defroster depends on the model of the refrigerator, but in most units with the No Frost system it is located in the freezer camera, behind the back panel. To get to it, you will have to perform partial disassembly.
First, remove all shelves, drawers and containers from the freezer. Then remove the back plastic panel that covers the evaporator. It can be secured with screws or plastic clips. Be careful: plastic becomes brittle in the cold and can crack if handled carelessly.
After removing the panel, you will see the evaporator (radiator with tubes) and a heating element located nearby. It may look like a curved tube encircling the bottom of the radiator, or it may be built into the plastic body of the tray. In some models Indesit or Atlant the heater is hidden deep and requires removal of the evaporator itself.
To visually assess the condition, inspect the heating element. If it shows swelling, cracks, signs of corrosion or melted insulation, this is a clear sign of a malfunction. However, the element often looks intact from the outside, and the problem can only be identified with a device.
Multimeter testing technology
The most reliable way to check the functionality is to measure the circuit resistance. To do this, switch the multimeter to resistance measurement mode (limit 2 kOhm or 20 kOhm). If you have a “dialing” mode with a sound signal, you can use that, but digital resistance values will give a more accurate picture.
Disconnect the wire terminals from the heating element contacts. Do not test an element connected to the refrigerator circuit, as the readings will be distorted by parallel connections. Press the multimeter probes onto the heater contacts. Polarity in this case does not matter.
The normal resistance of a working heating element is usually in the range from 200 to 600 Ohm. The specific value depends on the power of the element and the model of the refrigerator. For example, for a standard heater with a power of 300-400 W, the resistance will be about 150-250 Ohms. If the screen displays a unit (infinity) or a break sign, it means that the nichrome thread inside has burned out.
It is also necessary to check that there is no short circuit to the body. Press one probe to the contact of the heating element, and the second to the metal tube or heater body. The multimeter should show infinity (break). If the device beeps or shows any resistance value, it means that a current leak has occurred on the housing.
⚠️ Attention: A breakdown on the heating element housing is a direct threat to life! Using such a refrigerator without replacing a part is prohibited, since the entire body of the unit may be energized.
Sometimes the resistance of the heating element may be normal, but it does not work due to oxidation of the contacts at the junction with the wires. Clean the contacts and check the reliability of the connection. In some cases, oxides create a high contact resistance, which interferes with normal operation.
Analysis of results and table of values
After taking measurements, it is necessary to correctly interpret the data obtained. The numbers on the multimeter screen tell more about the internal condition of the heating element than an external inspection. Below is a table that helps decipher the readings of the device.
| Multimeter reading | Diagnosis | Actions |
|---|---|---|
| 200 - 600 Ohm | Good | Look for the cause in the timer, defrost sensor or wiring. |
| 1 (infinity) | Open circuit | Replacement of heating element required (defroster). |
| 0 Ohm (or close to 0) | Short circuit | The heating element needs to be replaced, the circuit fuse may have blown. |
| Any value when measured on the body | Insulation breakdown | Urgent replacement of the heating element, operation is dangerous. |
If the multimeter shows a break, this means that the nichrome spiral inside the tube has burned out. It cannot be restored; you need to purchase a new item. When ordering spare parts, pay attention not only to the model of the refrigerator, but also to the geometric dimensions and power of the old heating element.
It can be built into the circuit in series with the heating element or located nearby. If the heating element itself rings normally, but no current passes, be sure to check this small cylindrical element. Its resistance should be zero (or very close to it).
What to do if the heating element is working?
If the heater is intact and defrosting does not occur, check the defrost sensor (defrost thermostat). It should open the circuit when heated. Also check the defrost timer or the electronic control module, which sends a command to turn on the heating element.
Replacing a burnt-out defroster
The process of replacing a heater is not very complicated, but requires care. After you are convinced that the old part is faulty, remove it. Fastenings can be different: screws, staples, or simply fitting into grooves. In some models Samsung or LG The heating element is inserted into a special groove under the evaporator.
The new element is installed in place of the old one. Make sure it fits snugly against the surface it is supposed to heat. If there is an air gap between the heating element and the evaporator, the defrosting efficiency will decrease and ice will begin to accumulate again.
Connect the wires. If the old terminals have oxidized or melted, it is better to replace them with new ones. To ensure a secure connection, you can use heat shrink tubing to protect the contacts from moisture. Assemble the back panel and install the shelves in place.
After assembly, turn on the refrigerator. The first defrost cycle may not occur immediately, as the electronics need time to analyze the temperature. Let the unit operate for several hours so that it reaches the desired temperature before making final conclusions.
Typical diagnostic errors
Beginners often make mistakes that lead to false conclusions. One of the most common is checking the heating element without disconnecting it from the general circuit of the refrigerator. In this case, the multimeter can show the resistance of other parallel-connected elements, and you will decide that the heater is intact.
Another mistake is ignoring the condition of the wires. Even if the heating element itself is working properly, a break in the wire in the harness that goes to the connector will lead to the same result - no heating. Always “ring” the entire circuit from the connector to the heater contacts.
- 🔌 An attempt to check the resistance on a “hot” refrigerator when the heating element is still warm (resistance can change depending on the temperature).
- 💧 Moisture gets on the multimeter probes or contacts, which gives false leakage readings.
- 🛠 Using a faulty or discharged multimeter, the readings of which cannot be trusted.
It is also worth mentioning that in some modern models the heating element is controlled directly from the electronic module. If the module freezes or burns out, voltage will not be supplied to a working defroster. In such cases, diagnostics require checking the presence of voltage at the terminals of the heating element during the defrost cycle.
⚠️ Attention: The design of refrigerators from different brands may differ significantly. In some models, access to the heating element requires complete defrosting within 24 hours, otherwise the plastic or evaporator tubes may be damaged during dismantling.
Is it possible to temporarily use a refrigerator without a defroster?
Technically, the refrigerator will freeze, but only until the evaporator is completely covered with ice. This will happen in 1-3 days. After this, the air circulation will stop, the compressor will work non-stop, trying to cool the chamber, which will lead to its overheating and failure. Ice can also block the door or damage food. Operation in this mode is only possible in emergency mode for a short time.
Why does the defrost heating element burn out?
The main reason is the natural wear of the nichrome spiral during cyclic heating and cooling. Also, rapid failure is caused by corrosion (if the integrity of the heating element shell is damaged), voltage surges in the network or a malfunction of the defrost sensor, which causes the heater to work for too long, overheating beyond the norm.
Which heating element is better: aluminum or quartz?
Aluminum heating elements are more common, cheaper and give off heat better in less time counting the contact area. Quartz (in a glass or ceramic tube) are considered more durable and protected from corrosion, but they are more expensive and often have a different mounting design. It is best to install an original spare part or a high-quality analogue recommended by the manufacturer of your refrigerator model.
Is it necessary to change the thermal fuse along with the heating element?
If the cause of the combustion of the heating element was a power surge or short circuit, the thermal fuse could have tripped and burned out too. In most cases, when replacing the heating element, it is recommended to change the thermal fuse (defrost thermostat) preventively, since it is inexpensive, and its failure will again stop the defrosting system.