The refrigerator stopped freezing, but a puddle appeared inside or, conversely, all the food was covered with frost? Often the culprit of such troubles is compressor, which is the heart of the entire cooling system. You can understand whether this unit is working normally or requires replacement by paying attention to a number of indirect signs, without immediately resorting to complex tools.
However, relying only on external sensations is risky, since the symptoms may overlap with malfunctions of the thermostat or freon leakage. In this article we will look in detail at how to carry out initial diagnostics, what to look for during a visual inspection and how to use multimeter to accurately check the electrical parameters of the engine.
Timely identification of the problem will avoid damage to a large number of products and costly repairs of the entire system. If you hear strange clicks or the engine hums but does not start, you must immediately begin diagnostics in order to prevent complete failure of the equipment.
Visual diagnostics and sound analysis
The first stage of testing always begins with a careful inspection and listening to the operating unit. Go to the refrigerator and listen: a working compressor emits a steady, quiet hum that may be interrupted periodically when the system reaches the set temperature. If you hear a loud metallic knock, ringing or intermittent humming, this is a sure sign of a mechanical breakdown inside the compressor motor. Pay attention to the frequency of operation. The normal mode is when the refrigerator runs for about 15-20 minutes, followed by a pause. If the engine turns on for just a few seconds, a click is heard and it turns off again, this indicates that the thermal relay has tripped or there is a problem with the starting mechanism. motor-compressor.
Pay attention to the frequency of work. The normal mode is when the refrigerator runs for about 15-20 minutes, followed by a pause. If the engine turns on for just a few seconds, a click is heard and it turns off again, this indicates that the thermal relay has tripped or there is a problem with the starting mechanism.
⚠️ Attention: If, when you try to start, the compressor makes a loud click and immediately goes silent, do not try to turn it on repeatedly. This can lead to burning of the windings or melting of the wiring.
A visual inspection of the rear of the unit is also important. Remove the protective cover (if there is one) and look at the compressor itself and the pipes coming from it. There should be no traces of oil, soot or swelling. The presence of oily stains often indicates a violation of the seal of the case, which makes further operation impossible without replacing the unit.
Checking the operating temperature conditions
One of the key indicators of serviceability is the ability of the system to maintain the specified temperature conditions. If the compressor works almost without stopping, and the temperature in the main chamber does not drop below +10..+12 degrees, this is an alarming signal. In such a situation refrigerant it may be evaporated, or the motor itself has lost its performance and is not able to create the necessary pressure in the system.
You can check the efficiency of operation using a regular thermometer by placing it in a glass of water in the central part of the chamber. Record the readings after 2-3 hours of operation. If during this time the temperature has not dropped to at least +5..+7 degrees with the engine running, it means that the cooling cycle is broken.
A common mistake is to ignore overheating of the case. Touch the rear grille or the compressor itself (careful, it may be hot!). If the body is hot to the point where it is impossible to touch it, and the refrigerator does not freeze, this indicates an overload or an interturn short circuit in the motor windings.
Diagnostics of the starting relay and electrical circuit
Before sinning on the motor itself, it is necessary to rule out a malfunction of the starting relay. It is this small element that provides the initial impulse to start the engine. If the relay is faulty, the compressor will try to start, hum, but the shaft will not rotate, after which the protection will work.
To check the relay, it must be removed from the compressor contacts. Visually inspect the housing for melting or blackening. If the element is externally intact, it can be checked by shaking it near the ear: the presence of rattling indicates that the internal contacts are damaged or displaced.
The electrical circuit is also checked for integrity. Make sure the power cord is not damaged and the plug is intact. Often the problem lies in a banal lack of contact in the socket or in a malfunction of the thermostat, which simply does not send a command to turn on the motor.
☑️ Checking the starting relay
If after replacing the relay the situation has not changed, and the motor still hums for a couple of seconds and turns off, most likely the problem is deeper and lies in the electric motor or mechanical jamming of the piston group.
Instrumental check with a multimeter
The most accurate way to check the serviceability of the compressor in the refrigerator is to use multimeter. This device will allow you to measure the resistance of the windings and identify short circuits or open circuits that are not visible during external inspection.
First you need to remove the protective casing and disconnect the wires from the compressor contacts. Switch the multimeter to resistance (Ohms) measurement mode. First, check the circuit for breakdown on the housing: touch one probe to any contact, and the other to the copper tube or unpainted part of the housing. The device should show infinity (one in the most significant digit). If any resistance value is visible, it means that current has leaked to the housing, which is life-threatening.
Next, we check the resistance between the contacts. A standard single-phase compressor has three of them: general, starting and working. The resistance between the common and working contacts should be the smallest, between the common and starting contacts - average, and the sum of these two values should be equal to the resistance between the starting and working contacts.
| Pair of contacts | Normal resistance (Ohm) | Fault symptom |
|---|---|---|
| General - Working | 10 - 25 Ohm | Open (infinity) or short circuit (close to 0) |
| General - Starting | 20 - 40 Ohm | Open circuit or interturn short circuit |
| Starting - Working | 30 - 60 Ohms (sum) | Inconsistency with the sum of the other two |
| Contact - Housing | Infinity (∞) | Any value (insulation breakdown) |
Even a small deviation from the norm may indicate degradation of the winding insulation, which will soon lead to a complete failure of the equipment.
Why multimeter readings can "float"?
If you have just turned off the refrigerator, the resistance of the windings may be lower due to heating. Allow the compressor to cool for 30-40 minutes before taking accurate measurements. Also, the readings may be affected by oxidation of the contacts, which need to be cleaned before testing.
Mechanical faults and pressure
If the electrical part is in order, but the refrigerator does not freeze, a mechanical breakdown may have occurred. A valve inside the compressor may break or the piston group may collapse. In this case, the motor will operate silently or with a very quiet hum, without creating characteristic vibration.
You can check the presence of pressure by disconnecting the discharge pipe (only for experienced craftsmen with the appropriate equipment!). When the engine is running, a strong air flow should be felt from the tube. If the flow is weak or absent, the compressor does not pump.
⚠️ Attention: You can only open the system and disconnect the tubes if you have a license to work with freon and special equipment. Independent release of refrigerant into the atmosphere is prohibited by law in many countries.
Another sign of mechanical failure is the so-called “jamming”. If the motor shaft is stuck, the start relay will continually click, trying to start the motor, but the shaft will not budge. In some cases (rarely), “wedging” by applying increased voltage helps, but at home this method is extremely dangerous and is not recommended.
When a compressor replacement is necessary
Replacing a compressor is a complex and expensive process that requires evacuation of the system and refilling the refrigerant. The decision to replace should be made only after all other faults have been excluded: the thermostat has been checked, the start relay has been replaced, making sure there are no freon leaks.
The main reasons for replacement: breakdown of the windings to the housing, interturn short circuit, mechanical jamming of the shaft or loss of performance (the compressor works, but does not create the required pressure). In these cases, repairing the old motor is not economically feasible.
When choosing a new unit, pay attention not only to the dimensions, but also to the type of refrigerant (R134a, R600a), power and type of oil. Installing an unsuitable compressor can lead to rapid failure of the entire refrigeration system.
Frequently asked questions (FAQ)
Can a faulty compressor consume more electricity?
Yes, if the compressor is running continuously due to loss of performance or freon leakage, it will consume significantly more electricity trying to reach the set temperature. Also, increased consumption may occur due to an interturn short circuit.
Why is the compressor hot, but the refrigerator does not freeze?
This may indicate several problems: a freon leak (the motor overheats from continuous operation), a blockage in the capillary tube or loss of compression (mechanical failure inside the motor).
How long does a compressor last in a refrigerator on average?
The service life of a modern compressor is from 10 to 15 years if the operating rules are followed. However, frequent voltage drops in the network or improper defrosting can significantly shorten this period.
Is it possible to repair an old compressor or just replace it?
In domestic conditions, compressors are considered beyond repair. Their body is sealed, and repairs require special equipment for opening, replacing internal components and resealing, which is usually more expensive than buying a new unit.