Modern LG refrigerators, equipped inverter compressors, are famous for their energy efficiency and quiet operation, but their electronic filling requires a special approach when diagnosing. Unlike old linear motors, there is no conventional starting relay, and starting and speed control are carried out through a complex inverter board, which often confuses home repairers when trying to find a fault.
The initial check begins with a visual inspection and basic measurements of winding resistance, which eliminates a mechanical wedge or an obvious break circuit. Multimeter becomes the main tool in the hands of a specialist, allowing you to determine in a matter of minutes whether the unit itself is alive or the problem lies in the control electronics.
It is important to understand that thoughtless replacement of parts may not solve the problem if it is not carried out competently diagnostics the entire power circuit. In this article, we will analyze in detail the algorithm of actions that will help you accurately determine the condition of the compressor and avoid unnecessary expenses on purchasing a new unit.
Principle of operation and difference from linear models
The inverter motor in LG refrigerators works on the principle of changing the shaft speed, which allows you to maintain a given temperature without constant stopping and starting at full speed. The main difference is the presence of a built-in control board and the absence of a classic starting relay, which often failed in older models.
Traditional linear compressor either turned on at full power or turned off, while the inverter smoothly regulates its performance. This is achieved by converting direct current into alternating current with a variable frequency, which requires the serviceability of not only the mechanical part, but also the electronic components.
⚠️ Attention: An attempt to start an inverter compressor directly, bypassing the inverter board, is impossible and will lead to breakdown of the unit, since it does not have starting winding in the classical sense.
Understanding this difference is critically important, since the testing methods winding resistance here are similar to the classical ones, but checking functionality requires analysis of control signals. If in a conventional motor we are looking for a short circuit between the contacts, then here we add the factor of interaction with the inverter unit.
Required tools and safety measures
Before starting any diagnostic work, you must ensure complete safety, since you will be working with high voltage and complex electrical equipment. A basic set of tools includes a digital multimeter with a continuity function, a set of screwdrivers, insulating tape and, preferably, a current clamp for a more in-depth analysis.
Be sure to disconnect the refrigerator from the electrical outlet before removing the back panel and accessing the compressor compartment. Even after disconnection, a residual charge may remain in the capacitors of the inverter unit, so do not touch the board contacts with bare hands immediately.
- 🛠️ Digital multimeter with measurement accuracy up to 0.1 Ohm for checking the integrity of the windings.
- 🔌 Insulated probes and dielectric gloves for protection against damage current.
- 💡 A flashlight or additional lighting, since the compressor compartment is often darkened.
- 📋 Connection diagram for a specific LG refrigerator model for checking the color markings of the wires.
The use of high-quality measuring device guarantees the accuracy of the readings, since cheap testers can give a significant error when measuring small resistances. Also make sure that the work area is dry and well lit to avoid accidental short circuits.
☑️ Preparing for diagnostics
External inspection and access to contacts
To take measurements, you need to gain access to the contact group of the compressor, which is usually covered with a plastic casing or located under the protective cover. Remove the back panel of the refrigerator by unscrewing the mounting screws and carefully inspect the condition of the wires for melting, darkening or mechanical damage.
On the body of the LG inverter compressor there is often a sticker with technical information, which indicates the model, type of refrigerant and electrical parameters. Check if there are any traces of oil on the body of the unit itself, which may indicate a violation of the tightness of the system, which makes further electrical diagnostics pointless.
Carefully remove the plastic cover from the contact group, having previously photographed the location of the wires so as not to confuse them during assembly. The contacts must be clean, without oxides and deposits, which could distort the resistance readings.
| Parameter | Normal value | Fault symptom |
|---|---|---|
| Winding resistance | From 5 to 15 Ohm (between phases) | Open (infinity) or short circuit (0 Ohm) |
| Resistance to body | Infinity (1) | Any value (breakdown insulation) |
| Appearance of the wires | Complete insulation, no blackening | Melting, cracks, burning smell |
If a visual inspection reveals burnt wiring or a melted connector, this may indicate poor contact or overload caused by a malfunction the inverter module itself.
Checking the resistance of the windings with a multimeter
The main diagnostic stage is to measure the resistance between the contacts on the compressor block. LG inverter compressors typically have three-phase windings, so the pins are often labeled U, V, W or color-coded (e.g. red, white, blue).
Switch the multimeter to resistance (ohm) mode with a 200 ohm limit. Alternately apply the probes to pairs of contacts: first-second, second-third, first-third. The readings should be approximately the same for all pairs, which indicates the integrity of all three phases.
The spread of values should not exceed 5-10%; if the difference is significant, it means that one of the windings has a defect or an interturn short circuit. Ideally, the resistance of each pair of contacts should be in the range from 5 to 15 Ohms; it is better to check the exact data with the service documentation for a specific model.
What to do if the readings are different?
If the resistance of one of the pairs is significantly lower than the others, this is a sign of an interturn short circuit. Such a compressor will consume increased current and quickly overheat, requiring replacement.
A critical point is to check that there is no short circuit to the housing. Press one multimeter probe to any contact of the block, and the second to a cleaned place on the metal body of the compressor.
The device should show one (infinity), which means there is no electrical connection. If you see any resistance values, this indicates insulation breakdown, and the operation of such a unit is deadly.
Diagnostics of starting current and inverter operation
If winding resistance measurements showed normal, but the refrigerator does not turn on or the compressor hums and goes silent, the problem may lie in the starting current or a malfunction of the inverter board. For accurate diagnostics in dynamics, you will need a current clamp that allows you to measure the current consumption without breaking the circuit.
When you try to start, a working inverter compressor should smoothly pick up speed, and the current consumption should not jump sharply. A sharp surge of current and subsequent shutdown usually indicate that the protection in the inverter unit has tripped due to a compressor wedge or an electronic malfunction.
- 📉 Normal starting current gradually increases and stabilizes.
- 📈 A sharp jump in current to the maximum and shutdown is a sign of a wedge or Short circuit.
- 🔇 Lack of response and silence - a problem with the control signal or inverter power supply.
A common mistake is replacing the compressor when the motor is working, but the control board is burnt out. The inverter unit may generate an error if the Hall sensors inside the compressor are reporting incorrect rotor position data.
Typical diagnostic errors and their consequences
One of the most common mistakes is an attempt to “revive” the compressor by applying voltage directly, bypassing the electronics. As already mentioned, inverter motor cannot start without a frequency-forming signal, and such a procedure is guaranteed to disable it.
Also, technicians often ignore checking the integrity of the wires going from the board to the compressor. A break in the harness or oxidation in the connector can simulate a malfunction of the unit itself, creating a false impression of a winding break.
⚠️ Attention: Never check the resistance of live windings! This will instantly damage your multimeter and may result in electric shock.
Incorrectly setting the measurement limits on the multimeter will also lead to incorrect conclusions. If the device shows “1” at the 200 Ohm limit, this is not always a break - perhaps the resistance is simply higher than the measurement limit, and you need to switch the range.
Interpretation of the results and the final decision
After all measurements are taken, it is necessary to compare the obtained data with the standard values. If the resistance of the windings is normal, there is no breakdown to the housing, but the compressor does not start, it is highly likely that the refrigerator control module or the inverter unit is faulty. how rewinding such sealed units is economically impractical and technically difficult. Repair of the cooling system with replacement of the compressor requires evacuation and refilling with refrigerant. inverter unit or refrigerator control module.
If an interturn short circuit or a breakdown in the housing is detected, the compressor must only be replaced, since rewinding such sealed units is economically impractical and technically difficult. Repair of the cooling system with replacement of the compressor requires evacuation and charging with refrigerant.
If the diagnostics showed the serviceability of the electrical part of the motor, but the problem persists, you should pay attention to the heat removal system and the cleanliness of the condenser. Overheating can trigger thermal protection, simulating an electrical breakdown.
A competent approach to diagnostics allows you to save significant money by accurately identifying the culprit of the malfunction. Remember that the electronics of LG refrigerators are sensitive to voltage surges, so using a stabilizer can extend the life of your equipment.
Frequently asked questions (FAQ)
Is it possible to check the inverter compressor without removing it from the refrigerator?
Yes, an initial check of the winding resistance and The absence of a breakdown on the housing can be carried out without removing the compressor. However, to measure starting currents and detailed diagnostics of operation under load, it may be necessary to access the rear of the unit and remove protective covers.
What resistance values are considered normal for LG compressors?
For most LG inverter compressors, the resistance between the winding contacts (U-V, V-W, U-W) must be symmetrical and be in the range from 5 to 15 Ohms. The exact values depend on the power of the specific model and the temperature of the windings.
What to do if the multimeter shows “0” between the contacts?
The reading “0” Ohm indicates a short circuit in the winding turns. This is a serious malfunction in which the compressor will not work, and when trying to start, the circuit breaker will trip or the inverter board will burn out. The unit needs to be replaced.
Why does the compressor start and immediately stall?
This can be caused by several reasons: activation of the thermal relay due to overheating, a wedge in the mechanical part of the compressor, a malfunction of the inverter board or low voltage in the network. Consistent diagnostics of all components is necessary.