Failure of a refrigerator to work is always stressful, because food supplies are at risk. Most often, the cause of the breakdown is precisely compressor, which is the heart of the entire cooling system. If you notice that the unit is humming but not cooling, or, conversely, is standing in complete silence, it is necessary to carry out an initial diagnosis.
Before calling a technician or looking for a replacement, it is worth understanding whether the problem really lies in the motor. Electrical circuit may be broken, the starting relay could burn out, but the compressor itself remains intact. Correct diagnostics will save money and time, eliminating the unnecessary purchase of an expensive unit.
In this article we will analyze in detail the algorithm of actions that will help determine the technical condition of the engine. We will look at visual inspection methods, methods for checking windings with a multimeter and the nuances of starting the device directly.
Primary diagnostics and visual inspection
Any diagnostics begins with an external examination and analysis of the behavior of the equipment. If the refrigerator has stopped freezing, first of all listen to its operation. Working compressor it emits a smooth, monotonous hum that periodically subsides when the cycle stops. Lack of sound or an intermittent hum followed by a click indicates a problem.
Carefully inspect the rear wall of the unit. There should be no traces of oil, burning or melted wiring in the motor area. The presence of oily stains is a sure sign that the seal of the housing is broken, and the compressor can only be replacedas it cannot be repaired at home.
⚠️ Attention: If you smell burning or see sparking in the compressor area, immediately turn off the device from the mains. Further operation may lead to a short circuit or fire.
It is also worth checking the temperature conditions. Touch the capacitor (grid on the back) and the motor itself. They should be warm or hot when working. If the motor is cold but the refrigerator is not running, there may be no voltage. If the motor is hot to the point where it is impossible to touch it, but there is no cold, there is overheating or jamming of the mechanism.
Checking the electrical circuit and starting relay
Before “climbing” into the motor itself, it is necessary to rule out a malfunction of the starting protection relay. This small block is responsible for supplying current to the windings and protecting against overloads. Often it is its failure that creates the illusion of a compressor failure. To check the relay, you need to carefully remove it from the motor contacts.
Visually inspect the insides of the relay: if traces of soot, melting or destruction of the contacts are visible, the part requires replacement. You can also shake the relay near your ear: if you hear the ringing of a broken “tablet” (thermal relay) inside, it means the element is faulty. In good condition, there should be no extraneous sounds.
Checking the integrity of the relay circuit is done using a multimeter in continuity mode. The contacts must “ring” in a certain position, corresponding to the instructions for a specific model. If the circuit is broken, the motor will not receive an impulse to start, even if it is fully operational.
- 🔌 Disconnect the refrigerator from the mains and remove the protective cover of the compressor.
- 🔧 Carefully disconnect the wires from the start relay, remembering their location.
- 👀 Inspect contacts for oxidation and check the integrity of the thermal relay.
- 📏 Test the circuit with a multimeter to make sure current is passing.
Diagnostics of motor windings with a multimeter
If everything is in order with the relay, we move on to the most important part - checking the windings electric motor. For this you will need a multimeter. On the body of most compressors there are three contacts: two working (starting and working windings) and one common. The location of the contacts depends on the model, but most often they form a triangle.
It is necessary to measure the resistance between each pair of contacts. The values will differ depending on the power of the motor, but the principle remains the same: the sum of the resistances of the starting and operating windings should be equal to the resistance between the extreme contacts. If the multimeter shows infinity (open circuit) or zero (short circuit), the winding is burned out.
Pay special attention to checking for breakdown of the housing. One multimeter probe is applied to any contact, and the second is applied to a cleaned area on the compressor housing (where there is no paint). The device should show infinity. Any other values indicate that Insulation is broken, and operating such a unit is deadly.
| Measurement type | Normal reading | Failure sign |
|---|---|---|
| Start winding | 20-50 Ohm (depending on the model) | Infinity or 0 Ohm |
| Working winding | 10-25 Ohm | Infinity or 0 Ohm |
| Breakdown to body | Infinity (∞) | Any digital values |
| Interturn short circuit | Stable resistance | Significantly below normal, burning smell |
What is an interturn short circuit?
This is a partial destruction of the insulation inside the winding. The multimeter may show the norm, but when voltage is applied, the current increases sharply, knocks out plugs or burns out the wiring. It can be determined only by indirect signs: strong heating and humming.
Method of direct start of the compressor
The most reliable method, how to check a refrigerator compressoris its direct start, bypassing the start relay. This method allows you to understand whether the engine is able to start and gain speed at all. For the procedure, you will need a piece of wire with a plug and, preferably, a new start relay or start button.
The essence of the method is to apply voltage directly to the working and starting windings. For a short moment (1-2 seconds), current is supplied to the starting winding to create torque, after which the power remains only on the working one. If the motor hums, but does not start, and the shaft does not spin, it may be jammed.
⚠️ Attention: Direct starting is dangerous due to electric shock! Perform all manipulations with live wires only with dielectric gloves and using tools with insulated handles.
If, with a direct connection, the compressor starts confidently and begins to pump air (check by blowing into the outlet tube), then the problem was in the relay or thermostat. If the motor hums, jerks and knocks out the circuit breaker, but does not start even with a “kick,” there is likely a hydraulic wedge or critical wear of the mechanical part.
☑️ Checking the motor start
Analysis of pressure and performance
Sometimes the electrical part is working properly, the windings are intact, the motor starts, but there is no cold. In this case, the ability of the pump to create the required pressure in the system is checked. For an accurate diagnosis, a pressure gauge station will be required, but a rough estimate can be given without it. compression — the ability of the pump to create the required pressure in the system. For an accurate diagnosis, a pressure gauge station is required, but a rough estimate can be given without it.
When the compressor is running, a strong air flow should be felt at the outlet of the discharge tube. If you put your finger near the hole, the stream should noticeably blow it away. Weak flow or no flow indicates that the valves inside the cylinders are worn out or burnt out. In this case, the motor runs idle.
You should also pay attention to the suction tube. During normal operation, it should cool slightly and even become covered with condensation. If the system is open (the tubes are cut), a confident air intake should be felt at the inlet with the palm of your hand. The lack of suction effect indicates a mechanical breakdown of the piston group.
- 💨 Blow into the tubes: air should flow with resistance only in one direction (through the valves).
- 🌡️ Check the temperature: the discharge tube heats up quickly, the suction tube cools down.
- 👂 Listen to the sound: a uniform hissing of the valves is normal, a metallic clang is pathology.
Frequent causes of failure and prevention
Understanding the causes of failure will help extend the life of new equipment. Most often compressors they fail due to overheating caused by poor ventilation or contamination of the condenser. Dust, animal hair and fluff, settling on the grille at the back, create a “thermal coat” that prevents the freon from cooling down.
Another common reason is frequent voltage drops in the network. Current surges destroy the insulation of the windings and burn out the relay contacts. Using a voltage stabilizer or at least a surge protector with protection can save an expensive unit. Frequent switching on and off is also harmful, so do not place the refrigerator near heat sources.
Regular cleaning behind the refrigerator and checking the tightness of the doors is a simple but effective preventive measure. If the door does not close tightly, the compressor is forced to work almost without stopping, which leads to accelerated wear and eventual failure.
Is it possible to restore a jammed compressor?
In rare cases, if the jamming is caused by prolonged downtime and thickening of the oil, the “swinging” method helps. The windings are supplied with increased voltage (through a transformer) in short-term pulses. However, this method is risky and often leads to the final burning of the windings. In most cases, it is easier and more reliable to replace the unit.
Why may a new compressor fail to start?
The reason may be incorrect installation of the start relay, mixed up contacts or insufficient voltage in the network. It is also important to make sure that there is freon in the system: many modern models have pressure switches that block startup if there is no pressure in the circuit, in order to avoid running “dry.”
How long should the compressor operate normally?
The operating time depends on the load of the refrigerator, the room temperature and the thermostat settings. Typically the cycle is from 10 to 30 minutes of work and the same amount of rest. If the motor runs without stopping for hours, this is a sign of a freon leak, a loss of seal in the chamber, or a malfunction of the compressor itself.