Modern refrigerators with a system No Frost or Low Frost are equipped with a complex defrosting system, the key element of which is a tubular electric heater. If you notice that a fur coat is growing on the back wall of the freezer, and the fan is humming due to blockage by ice, most likely the problem lies in this unit. Diagnostics begins with a visual inspection, but only a measuring device can make the final verdict.
Many owners of household appliances mistakenly believe that the lack of heating indicates a burnt-out thermostat or a faulty timer, forgetting to check the heating element itself. Ring the heating element This is a basic procedure available to any home craftsman who has a multimeter at hand. It allows you to determine with 100% accuracy whether you need to buy a new part or look for the cause in the electrical control circuit.
In this article we will analyze in detail the algorithm of actions, the necessary safety measures and the interpretation of the device readings. You will learn which resistance values are considered normal and which indicate a breakdown or break. Understanding these nuances will save you time on calling a technician and money on diagnostics.
Preparation for diagnostics and safety measures
Before you begin any manipulations with electrical equipment, you must completely turn off the power to the refrigerator. Unplug the power cord and ensure that electrical components are safe to access. Any work inside the case is possible only after you remove the back panel of the freezer, where the evaporator with the heater is usually located.
To carry out diagnostics, you will need a digital multimeter capable of measuring resistance (Ohm) and checking the continuity of the circuit (continuity mode). You may also need screwdrivers to remove the panels and, possibly, a hair dryer to speed up defrosting if the ice completely hides the contacts of the heating element.
⚠️ Attention: It is strictly forbidden to measure resistance on an energized element. This will cause immediate failure of the multimeter and can be life-threatening.
Make sure your hands are dry and the floor under your feet does not conduct electricity. If the refrigerator has just been running and has been unplugged, wait a few minutes to allow the capacitors in the electronic control module, if equipped, to discharge. Safety is the foundation of quality repairs.
After removing the panel, evaluate the condition of the evaporator. If it is covered with a thick layer of ice, do not try to chip it with a knife, as you may damage the aluminum tubes or the heating element itself. It is better to let the ice melt naturally or carefully use warm air.
Removing the heating element
To ring the heating element, it does not have to be completely removed from the refrigerator, but access to its contact terminals must be free and clean. In most models Indesit, LG or Samsung the heater is a curved tube that goes around the evaporator, or a U-shaped element inserted into special grooves.
First, disconnect the connectors going to the heater. They can be protected with plastic casings or sealed with sealant. Carefully free the contacts from moisture and oxides, as dirt on the terminals can distort the readings of the device during testing.
If the heating element is mounted on brackets or in grooves, make sure that it is not closed anywhere to the body with metal fasteners. For accurate diagnostics, it is best to disconnect at least one wire from the heater contact to eliminate the influence of parallel circuits, although when measuring the resistance of the element itself, this is not always critical if the circuit is open.
Visually inspect the heating element body for swelling, cracks or traces of burning. Often malfunction visible to the naked eye: a deformed tube indicates local overheating and a possible internal break of the nichrome spiral.
Setting up the multimeter and testing method
For diagnostics, we need a resistance measurement mode, which is on the scale The device is indicated by the symbol Ω (Ohm). If your multimeter has automatic limit selection, simply switch it to this mode. In hand-held multimeters, select the limit of 2 kOhm (2000 Ohm) or 20 kOhm, since the resistance of household heating elements usually ranges from tens to several hundred Ohms.
Touch the two contacts of the heating element with the probes. It does not matter which probe (red or black) touches which contact, since the heating element is an active resistance without polarity. The main thing is to ensure reliable contact between the metal of the probe and the terminal of the heating element.
If the display shows a unit on the left (or an infinity symbol OL), this means an open circuit. The inner spiral has burned out and no current flows through it. Such a heating element can only be replaced, it cannot be repaired.
The second important stage of testing is the insulation breakdown test. Press one probe to any contact of the heating element, and the second to the metal body of the heater (clean a small area of oxides for better contact). In good condition, the device should show infinity, since nichrome should not be in contact with the ground.
☑️ Checking the heating element with a multimeter
Analysis of readings and table of resistance standards
Received The numbers on the multimeter screen need to be interpreted correctly. The resistance depends on the power of the heater and the network voltage. The higher the power, the lower the resistance, and vice versa. For refrigerators, the power of defrosting heating elements usually varies from 150 to 500 W.
There is a formula for calculation: R = U² / P, where U is voltage (220 V) and P is power. However, in practice it is more convenient to use reference data. Below is a table of approximate values for standard heaters.
| Heating element power (W) | Expected resistance (Ohm) | Element status | |||
|---|---|---|---|---|---|
| 150 - 200 | 240 - 320 | Normal | |||
| 250 - 350 | 140 - 200 | Normal | 400 - 500 | 90 - 120 | Normal |
| Any | Infinity (1 or OL) | Open (Faulty) | |||
| Any | 0 - 10 | Short circuit |
If your readings are close to the table values, then the integrity of the spiral is preserved. However, this does not yet guarantee 100% proper operation, since there may be problems with heat transfer or hidden insulation defects that only appear under voltage.
Pay attention to the spread of values. If one end of the heating element shows 100 Ohms, and when testing the other section (if there are two of them), the readings are very different, this may indicate degradation of the spiral material. In such cases, the element may work, but not for long.
Checking for insulation breakdown
The most dangerous fault that can be detected with a multimeter is breakdown to the case. In this case, the nichrome spiral inside the tube comes into contact with the metal shell. When such a refrigerator is connected to the network, a dangerous potential may appear on the case, and the circuit breakers in the panel may be knocked out.
To check, we switch the multimeter to the high resistance measurement mode (2 MOhm or 20 MOhm) or to the diode testing mode (sound test). We place one probe on the contact, the other on the metal tube of the heating element.
⚠️ Attention: Even a small resistance (less than 1-2 MOhm) between the contact and the body indicates a violation of the insulation. The operation of such a refrigerator is prohibited!
Often a breakdown occurs due to microcracks in the tube, where moisture gets in during defrosting. In a dry state, the device may indicate normal, but when the metal heats up and expands, the crack spreads and a short circuit occurs. Therefore, if in doubt, it is better to replace the part.
If the multimeter emits a beep when the probe contacts the body, then a breakdown is guaranteed. In this case, further diagnostics are pointless - immediate replacement is required.
Diagnostics of adjacent elements of the defrost system
If the heating element is working, but the refrigerator does not defrost, the problem may lie in other components of the circuit. The defrost system includes a defrost temperature sensor (defroster), a fuse and a timer (or electronic module). These elements are also checked with a multimeter.
The fuse should ring short (resistance close to 0 Ohm). If it shows a break, it must be replaced, but first make sure that the heating element does not cause a short circuit, which led to the fuse burning.
The defrost sensor at room temperature must have a certain resistance (usually 4-6 kOhm for Samsung or about 13 kOhm for LG). As it cools, its resistance changes. Checking the sensor requires knowledge of its temperature characteristics, but a simple “ring” for a break is also informative.
It is important to check the integrity of the wiring. Wires often break at bends or become bent during assembly and disassembly. Ring each section of the circuit from connector to connector to eliminate breaks in the cables.
Frequent errors in diagnostics
One of the common mistakes is checking “by weight” when the heating element is not cleared of ice and moisture. Water can create conductive bridges between the contacts, distorting the readings. Always dry the assembly thoroughly before diagnosing.
Another mistake is ignoring the condition of the contacts in the connectors. Copper oxides create additional resistance, which the multimeter can perceive as a malfunction of the heating element itself. Clean the contacts to a metallic shine.
Some technicians forget to check the voltage in the network at the moment when the defrost should start. If the heating element does not receive 220 Volts, then even a working heater will not work. Use a multimeter in AC Voltage mode to check the incoming current.
It is also worth mentioning the human factor: an incorrectly selected measurement limit on cheap multimeters can produce a strong error. Always double-check the result by switching the range.
Replacing a faulty heater
If the diagnostics showed a break or breakdown, the heating element must be replaced. The selection of an analogue is carried out according to the markings applied to the metal tube or on the tag. Consider the geometric dimensions, power and method of fastening.
Installation of a new element is carried out in the reverse order of removal. Make sure that the heating element fits tightly into the evaporator grooves for efficient heat transfer. Do not use excessive force when bending the tubes; they are fragile.
After assembly, do not rush to close the panel. Turn on the refrigerator and forcefully start the defrost mode (if there is such a function in Service Mode) or just wait for the cycle. Check whether the heating element heats up and whether there is sparking in the contacts.
A high-quality replacement will return the system No Frost its functionality. Ice will stop accumulating, and the fan will operate silently again, ensuring proper air circulation.
Is it possible to restore a burnt heating element?
In the factory, a nichrome spiral is not restored. Theoretically, you can try to find the break point and weld the ends, but in everyday life this cannot be done reliably. In addition, a broken spiral geometry will lead to a change in resistance and rapid re-burnout. Repairing the heating element is not economically feasible.
Why does a new heating element burn out after a week?
If replacement does not help for a long time, look for the reason in the control circuit. The defrost timer contacts may be stuck and the heater is running continuously rather than cyclically. Also, the cause may be a faulty defrost sensor, which does not give a command to turn off the heating.
Which multimeter is better to choose for a home technician?
Any entry-level digital multimeter, for example, the DT-830 series or more modern analogues such as DT-9205A, is suitable for diagnosing household appliances. The main requirement is the presence of a dialing mode (sound signal) and the ability to measure resistance up to 20 kOhm.
Is a heating element with a breakdown to the body dangerous?
Yes, it is deadly. If the insulation breaks down, the metal body of the refrigerator may be under a voltage of 220 Volts. Touching this refrigerator, especially with wet hands or bare feet, may result in electric shock. Operation is prohibited.
Does humidity in the chamber affect the readings of the multimeter?
Yes, high humidity and the presence of water on the contacts can create parasitic leakage currents, due to which the device may show low resistance or the presence of a circuit where it should not be. Always wipe and dry the assembly before taking measurements.