Diagnostics compressor is the first and most important stage in restoring the functionality of the refrigeration unit. When the equipment stops cooling, but continues to hum or, conversely, remains silent, owners often look for a way to visually assess the condition of the motor through a smartphone camera. However, it is important to understand that no video can replace an instrumental check of electrical parameters. The internal processes occurring in electric motorare hidden from view, and relying only on external signs means risking safety.
In this article we will analyze why popular videos on the Internet are often misleading (misleading), and show how correctly combine visual inspection with technical measurements. You will learn what nuances professional craftsmen pay attention to when making nodes, and why a simple test with a tester may not reveal an interturn short circuit. The text will help you avoid common mistakes during diagnostics. defects nodes, and why a simple tester may not reveal an interturn short circuit. The text will help you avoid common diagnostic mistakes.
Before proceeding with disassembly, it is necessary to completely de-energize the unit. Electric current in combination with refrigerant creates a potentially dangerous situation. We will consider an algorithm of actions that will allow us to determine the malfunction with a high degree of probability without resorting to the services of a service center, but at the same time maintaining vigilance.
Visual assessment of the condition of the compressor
The initial inspection begins long before removing the casing. If you search the Internet for the query “how to check a refrigerator motor video,” then most likely you are interested in what a working motor looks like in operation. You can visually assess starting relay the motor housing itself by paying attention to the characteristic signs of a malfunction. Often problems are indicated by oil leaks, swelling or obvious mechanical damage.
Pay attention to the color and condition of the wires going to the contact group. If the insulation is blackened or melted, this is a sure sign of overheating or a short circuit. In such cases, further operation without replacing the unit is impossible and even dangerous. Thermal protection could work multiple times, which led to degradation of materials.
⚠️ Attention: If you notice a burning smell or see traces of soot on the back wall of the refrigerator, immediately stop trying to start engine. This may indicate a critical condition of the winding insulation.
Many users try to shake the compressor to hear the sound of the valves coming off. This method has a right to exist, but it does not guarantee accuracy. A dull knock may be a sign that valve group has been destroyed and the piston is hitting the cylinder walls. However, sometimes the sound is made simply by refrigerant or oil dangling inside, which is not a fatal failure.
Instrumental diagnostics with a multimeter
The most reliable way to check is using multimeter. Videos often show this process in an accelerated manner, omitting important details of setting up the device. First you need to gain access to the contacts by removing the plastic casing and disconnecting the start relay. You will need to measure the resistance between the terminals of the windings.
The motor body usually has contact markings: C (common), R (working winding) and S (starting winding). Switch the multimeter to resistance measurement mode (ohms) to the 200 ohms limit. Sequentially measure the resistance between pairs of contacts. Write down the results, they will be needed for analysis.
Normal resistance values depend on the power of the motor, but usually the starting winding has a higher resistance than the working winding. If the device shows infinity (one in the most significant digit), it means that the circuit is in break. If the resistance is close to zero, a short circuit has occurred. Both cases require replacing the compressor or professional rewinding, which is not economically feasible in domestic conditions.
☑️ Check with a multimeter
Analysis of the starting relay and protection
Often the cause of the failure is not itself the engine, and the attachments. The starting relay is responsible for briefly supplying voltage to the starting winding to create torque. If it is stuck or burnt out, the engine will hum but will not start. Visually, there should be no cracks or traces of carbon on the relay.
You can check the relay by gently shaking it near your ear. If you hear a ringing sound, it means that the internal mechanism (often the ball in the induction coil or the contacts) is broken. It is also worth checking thermal relay, which opens the circuit when overheated. It should "ring" short when cold.
Some models use solid-state starters (PTC). They have no moving parts, but fail due to disruption of the chemical structure of the tablet. They can only be checked by replacing them with a known-good analogue or by measuring the resistance, which should be small (tens of ohms), but not zero.
Table of typical resistance values
For ease of diagnosis, we present averaged data. Please remember that specific values may vary depending on the manufacturer (Danfoss, Secop, Embraco, Atlant) and the power of the unit. Resistance is measured at a winding temperature of about 25°C.
| Winding type | Resistance (Ohm) | Character malfunction | Probability of repair |
|---|---|---|---|
| Working (C-R) | 10 - 25 Ohm | Open or short circuit | Low |
| Starting (C-S) | 20 - 40 Ohm | Open or short circuit | Low |
| Between case and contacts | Infinity | Insulation breakdown | Zero |
| Thermal relay (cold) | 0 Ohm (closed) | Break circuit | High (replacement) |
If you get values very different from the tabulated ones, or the resistance “floats”, this is a sign of serious internal degradation. Interturn short circuit often manifested by unstable readings or heating of the windings when turned on for a short time.
Why can resistance change?
Copper resistance depends on temperature. As the windings heat up, the resistance increases. If, when warmed up with a hairdryer, the readings jump sharply or go to infinity, it means that there is a bad contact inside the coil, which breaks due to thermal expansion.
Checking for interturn short circuit
The most insidious malfunction is inter-turn short circuit. A standard multimeter can show normal resistance, since a few shorted turns have little effect on the overall resistance of a long winding. However, when voltage is applied, the current in the motor increases sharply, knocking out the circuit breakers or burning the wiring.
To identify this problem, professionals use special devices - short-circuited turn testers. At home, you can use the method of measuring current consumption. To do this, an ammeter is connected to the open circuit. When starting up, a working compressor consumes current corresponding to the rating data (usually 0.3–0.8 A for household models). If the current exceeds the norm by 2-3 times and immediately knocks out the protection, there is a short circuit.
⚠️ Attention: Measuring current under voltage 220V is dangerous to life. Unless you have experience working with electrical systems under load, do not perform this test yourself. Use current clamps with all safety precautions.
Another indirect sign is rapid and strong heating of the motor housing. If, after 1-2 minutes of operation after starting, the case heats up to a state where it is impossible to touch it, this is a sure sign of an interturn short circuit. A healthy engine heats up gradually and evenly. turn-to-turn short circuit. A working engine heats up gradually and evenly.
Typical errors in diagnostics
Trying to save money, owners often make mistakes that lead to the final breakdown of the equipment. One of the most common is an attempt to start “directly”, bypassing a relay, using a capacitor, or simply applying voltage to the working winding. This can lead to the winding burning out if the rotor jams.
It is also a mistake to ignore the condition of cooling system. If there is no freon in the system or it has come out due to a leak, the compressor will work non-stop, trying to gain temperature. As a result, it will overheat and burn out. Before checking the motor, make sure that the circuit is sealed.
You should not rely only on “video instructions”, where the process is shown under ideal conditions. In reality, the wires may be broken, the contacts may be oxidized, and there may be no grounding. Always double-check visually each step that you saw on the screen.
⚠️ Attention: Specifications and contact markings may vary depending on the year of manufacture and model of the compressor. Always check the official wiring diagram for your specific unit before starting work.
Frequently asked questions (FAQ)
Is it possible to check a compressor without a multimeter?
Quality check - no. One can only indirectly judge by the sound, heating and reaction of the circuit breakers. However, for accurate diagnostics and safety, you need at least a simple tester to check the integrity of the windings and the absence of a breakdown on the housing.
Why does the compressor hum, but does not start?
Most likely, the starting relay is faulty, the piston is jammed inside the cylinder, or an interturn short circuit has occurred, due to which there is not enough starting torque. Also, the reason may be low voltage in the network.
Which device is best suited for diagnostics?
A digital multimeter with a continuity test and resistance measurement function is optimal for a home technician. For professionals, megaohmmeters (to check insulation) and short-circuited turns testers are used.
Is it worth changing the compressor yourself?
Replacing a compressor requires not only electrical skills, but also the ability to work with the refrigeration circuit: evacuate the system, charge freon. This cannot be done without special equipment and skills, so after diagnosing the motor, a specialist is most often called.