A modern household refrigerator is a complex electromechanical unit, the failure of which often leads to food spoilage and financial losses. When the device stops cooling or starts working continuously, the first thing many owners suspect is a freon leak or a compressor failure, but often the problem lies in the electrical circuit. Using multimeter allows you to quickly and accurately determine the malfunction without calling a technician, saving a significant amount on diagnostics.
This universal measuring device is capable of checking the integrity of the motor windings, the operability of the starting relay, the serviceability of heating elements and the thermostat. Understanding the principles of operation ohmmeter and a voltmeter will help you distinguish a burnt out motor from a banal wiring break. In this article, we will analyze in detail the algorithms for testing each key component of the refrigeration unit.
To carry out high-quality diagnostics, you will need not only the tester itself, but also basic tools: screwdrivers for removing casings, pliers and, possibly, electrical tape for marking wires. Before starting any work it is absolutely necessary disconnect the refrigerator from the power supply, since working with a voltage of 220 Volts requires compliance with safety precautions.
⚠️ Attention: Before starting disassembly, make sure that the capacitors in the control circuit are completely discharged to avoid electric shock when touched contacts.
Preparation of the multimeter and safety precautions
Before you start testing the nodes, you must correctly configure the measuring device. Most modern multimeters have a rotary mode switch, which must be set to the resistance measurement position (Denoted as Ω or Ohm). For the initial check of circuit integrity, the “continuity” mode is often used, which emits a sound signal when the contacts are closed.
Make sure that the device probes are in good condition and their insulation is not damaged. When the probes touch each other, zero values or close to them should appear on the screen, and a squeaking sound should be heard. If the device shows one in the most significant digit or infinity, it means that the circuit is open or the probes are faulty. Zero calibration is an important step, especially for analog pointer models.
When working with electrical components of a refrigerator, it is important to be aware of the risks. Even after disconnecting from the network, some nodes may retain a residual charge. In addition, careless handling of the wires can lead to a short circuit the next time you turn it on. Always act calmly and consistently, checking every step.
Checking the integrity of the power cord and plug
Diagnostics of any electrical appliance, including a refrigerator, always starts with the simplest thing - checking the power supply. It often happens that the problem lies not in the inside of the unit, but in a damaged power cable or oxidized plug contacts. Kinks, damage to the insulation by pets or mechanical shocks can damage the integrity of the cores.
To check, disconnect the cord from the outlet and set the multimeter to the continuity mode. Press one probe to the pin of the plug, and the second to the corresponding contact at the entrance to the refrigerator (or at the end of the wire, if it is removable). The absence of a sound signal or the indication of infinite resistance will indicate a break inside the cable.
- 🔌 Checking the phase: check one of the plug contacts with the corresponding wire at the entrance to the device.
- ⚡ Check zero: check the second contact of the plug and the wire in the same way.
- 🛡️ Checking the grounding: if the plug has a third contact, make sure that it is intact to the body of the device.
If the cable has insulation damage, it must be replaced entirely, since twists and electrical tape are unacceptable in the humidity of the refrigeration chamber. It is also worth visually inspecting the place where the cable enters the refrigerator body - often this is where the wire breaks due to constant vibration of the compressor.
Diagnostics of the compressor and start relay
The heart of the refrigerator is the compressor, and checking it is the most important stage of diagnosis. The motor has three terminals: two for working windings and one common. To check the serviceability, you need to remove the rear protective cover and gain access to the motor contacts. Before testing, be sure to disconnect the wires from the terminals.
Switch the multimeter to resistance measurement mode (limit 2 kOhm or 20 kOhm). Measure the resistance between each of the three contacts. For a working motor, the sum of the resistances of the starting and operating windings should be equal to the resistance between the two extreme contacts. Typically, the values vary from 10 to 30 Ohms for the operating winding and slightly higher for the starting winding.
☑️ Checklist for checking the compressor
Pay special attention to checking for breakdown of the housing. Press one probe to any contact, and the second to a copper tube or an unpainted part of the compressor housing. The device should show infinity. If you see any resistance values, it means that something has happened short to housing, and the operation of such a refrigerator is deadly.
⚠️ Attention: If the compressor hums, but does not start, the problem may not be in the windings, but in a jammed mechanical part or malfunction of the starting relay.
The starting relay must also be checked. Shake it: if you hear a ringing sound, it means the core or contacts are broken. Ring the relay contacts in different positions - they should close and open when turned over (for posistor and electromagnetic relays, the logic must be looked at according to a specific type of circuit).
Testing heating elements and the No Frost system
In refrigerators with a system No Frost heating elements play an important role (heating elements), which are periodically turned on to defrost the evaporator. If the heating element burns out, the ice stops melting, the drainage becomes clogged, and the cold stops flowing into the chamber. Checking the heating element is carried out in the same way as checking the motor windings.
Find the heating element (usually it is hidden behind a plastic panel on the back wall of the freezer). Disconnect the wires from it and connect the multimeter probes to its contacts. A working heating element should show resistance in the range from 200 to 500 Ohms (the exact value depends on the power and model, for example, Indesit or LG).
| Element | Normal resistance | Failure sign | Action |
|---|---|---|---|
| Defrost heating element | 200 - 500 Ohm | Infinity (break) | Replacing the heating element |
| Dropper heating element | 300 - 600 Ohm | Short circuit to the body | Replacing the heating element |
| Thermal sensor | Depends on temperature | Does not change when heated | Replacing the sensor |
| Fuse | 0 Ohm (Sound) | Infinity | Replacing the fuse |
In addition to the heater itself, there is often a thermal fuse in the defrost circuit. Its task is to break the circuit if the temperature exceeds the critical temperature (usually 70-80°C), preventing a fire. Ring the fuse: it should “ring.” If the multimeter is silent, the element has burned out and requires replacement. data-i="116">Why does the heating element burn out?
Why does the heating element burn out?
A frequent reason for the failure of the heating element is long-term operation without water (dry) when the drainage hole is clogged. The ice does not have time to drain, the heater heats up and burns out.
Checking the thermostat and temperature sensors
Thermostat (thermostat) is a mechanical or electronic device that turns the compressor on and off depending on the temperature in the chamber. In older models it is a mechanical “twist”, in new ones it is electronic sensors. Checking a mechanical thermostat is simple: when warm, its contacts must be closed.
To check, remove the thermostat and connect the multimeter probes to its contacts. At room temperature, the device should show zero (short circuit). If you put the sensitive thermostat tube in the freezer for 5-10 minutes, the contacts should open (the resistance will go to infinity). Lack of response indicates a malfunction.
Electronic temperature sensors (NTC thermistors) change their resistance depending on the heat. They don't have a clear on/off point. Normal resistance at room temperature (+25°C) is usually around 5-10 kOhm. When cooling, the resistance should increase.
- ❄️ Freezing: place the sensor in the freezer and watch the multimeter readings change.
- 🌡️ Heating: hold the sensor in your hand - the resistance should smoothly decrease.
- 🔌 Contacts: check the wires going to the sensor for fractures at the base.
A faulty sensor can “lie” to the control module, causing the refrigerator to work without stopping or, conversely, not turn on at all. Replacing this element often requires selecting an analogue with an identical resistance coefficient.
Searching for current leaks and wiring diagnostics
One of the most insidious problems is current leakage on the refrigerator body. This may occur due to damage to the insulation of the wires inside the harness, moisture on the terminal blocks, or breakdown of the motor windings. This situation is life-threatening and requires immediate elimination.
To search for leaks, set the multimeter to the resistance measurement mode at the maximum limit (Megaohms) or to the insulation test mode, if the device allows it. Press one probe to the grounding contact of the plug (or the body), and with the other, sequentially touch all current-carrying parts inside the refrigerator.
Carefully inspect the wiring harnesses passing through vicino to the refrigerant pipes. Vibration can wear down the insulation and the wire will begin to touch the metal. Also check the mounting locations of lighting bulbs and defrost heaters - condensation often accumulates there, creating conductive paths.
Analysis of the operation of the fan and limit switches
In No Frost systems, the fan is responsible for circulating cold air. If it does not work, the evaporator becomes overgrown with ice, and the chambers become warm. The fan motor is also checked for winding resistance. Normal values usually lie within hundreds of Ohms or several kOhms, depending on the supply voltage (often 220V or 12V).
An important element is the door limit switch, which stops the fan when the chamber is opened. If the refrigerator hums when the door is open, the switch may be stuck. Ring its contacts: when the button is pressed (the door is closed), the circuit should be closed (for the fan circuit), when pressed, it should be open.
The test is performed in the dialing mode. Press the button with your finger or a door simulator and watch the readings change on the multimeter screen. Lack of response or “floating” resistance indicates the need to replace the limit switch.
What resistance standards are considered normal for a compressor?
For most household compressors, the resistance of the starting winding is 20-40 Ohms, and working - 10-25 Ohms. The exact values depend on the engine power and manufacturer (for example Danfoss, Atlant, LG). The main rule: the sum of the resistances of the two windings must be equal to the resistance between the extreme terminals, and the resistance to the housing must be infinite.
Why does the multimeter show one when checking the heating element?
A unit in the most significant digit (or the OL/1 symbol) means infinite resistance, that is, an open circuit. If you see this value when checking the heating element, it means that the nichrome spiral inside it has burned out. Such an element cannot be restored; a complete replacement is required.
Is it possible to check the control module of a multimeter?
It is impossible to fully check the functionality of the electronic module (control board) with a conventional multimeter at home. You can only check the integrity of the tracks, the presence of short circuits at the power input and the serviceability of the fuses. In-depth diagnostics of electronics requires an oscilloscope and specialized knowledge.
What to do if all components are working, but the refrigerator does not work?
If the multimeter shows the serviceability of all electrical circuits (windings, heating elements, sensors), but the refrigerator does not start, the problem may be mechanical (the compressor is jammed) or associated with a refrigerant leak. It is also possible that there is a hidden defect in the control module that does not supply voltage to the components. In such cases, you need to call a specialist with a pressure gauge manifold and experience in electronics repair.