A sudden stop of the refrigerator or, conversely, its endless hum often becomes an unpleasant surprise for the owner. In most cases, the cause of such anomalies is compressor the “heart” of the cooling system, which is responsible for the circulation of the refrigerant. Before calling a technician or buying a new unit, it is important to conduct an initial diagnosis to understand the scale of the problem.
Modern models, whether Indesit, Atlant or premium LG, are equipped with reliable motors, but they are also subject to wear. Understanding how to test a refrigerator compressor will allow you to save significant diagnostic costs and make informed repair decisions. In this article, we will analyze all stages of testing, from visual inspection to complex measurements of electrical parameters.
The first thing to do when a malfunction is detected is to evaluate the nature of the equipment’s operation. If the refrigerator has stopped freezing, but the light is on inside, this is already half the success in finding a breakdown. The absence of the characteristic hum of the motor when the power is on and the lamp is on most often indicates a problem with the starting relay or an open circuit, and not complete death of the engine.
Primary diagnosis: visual inspection and analysis sounds
The check should always begin with security and external analysis. Unplug the refrigerator, move it away from the wall, and remove the back panel to gain access to the motor. Carefully inspect the compressor housing for oil leaks, swelling or burning marks. Any visible damage to the insulation or housing requires immediate cessation of operation.
Sound diagnostics are also informative. A working unit emits a smooth, monotonous hum. If you hear a clicking sound, a metallic clanging sound, or an intermittent hum that ends abruptly, these are sure signs of mechanical or electrical problems. Often such sounds accompany problems with starting relay or jamming of the piston group.
⚠️ Attention: If, when you try to start, you hear a loud click, followed by silence, and this repeats cyclically, turn off the device immediately. This is a sign that the motor is trying to start, but cannot turn over, which will quickly lead to the windings burning out.
Pay attention to the temperature of the housing during operation. If the engine runs but remains cold, or, on the contrary, becomes hot to the point where it is impossible to touch it, these are alarming signals. Normal operating temperature varies, but should not cause a burn if briefly touched.
Instrumental check: use a multimeter
For deeper diagnostics you will need multimeter. This device will allow you to check the integrity of the windings and the absence of breakdown on the housing. Before starting any measurements, make sure that the refrigerator is unplugged for at least 15 minutes to allow the capacitors to discharge.
The first step is to remove the start relay and the protective casing from the compressor contacts. You will see three pins forming a triangle. You need to “ring” each pair of contacts. The normal resistance between the starting and working windings, as well as between them and the common wire, should be in the range from 10 to 30 Ohms, depending on the model.
- 🔌 Checking for open: If the multimeter shows infinity (one in the most significant digit) when measuring between any two contacts, this indicates a winding break.
- ⚡ Checking for a short circuit: Readings close to zero indicate an interturn short circuit, which requires replacing the motor.
- 🛡️ Checking for breakdown: One probe is placed on the contact, the second - on a copper tube or stripped metal of the housing. The device should show infinity.
If you find a breakdown in the body, you should absolutely not operate such a refrigerator. This creates a direct risk of electric shock. In such a situation, compressor can only be replaced, since it is impossible to restore the winding insulation at home.
Nuances of resistance measurement
The resistance of the windings may vary slightly depending on the engine temperature. A cold motor will show less resistance than a hot one. Therefore, if the readings fluctuate within 2-3 Ohms from the nominal value, this may be normal, but requires additional testing under load.
Checking the starting relay and capacitor
Often the compressor itself is working, and the problem lies in its starting system. Start relay responsible for sending an impulse to the starting winding, and then turns it off. If the relay is stuck or burnt out, the engine will not be able to start, although electricity will flow to it.
Remove the relay and shake it near your ear. If you hear the sound of broken glass or a loose core inside, the part is faulty. Also inspect the contacts for carbon deposits. To check, you can carefully apply power directly (only for experienced users!), bypassing the relay, but this must be done extremely carefully and briefly.
☑️ Diagnostics of the starting system
In models with capacitor starting, it is important to check the capacitor itself. Swelling of the housing or leakage of electrolyte are clear signs of failure. Even if it is visually intact, its capacity could have dropped, and the motor does not have enough energy to start. Replacing these elements is much cheaper than replacing the compressor itself.
⚠️ Attention: When directly applying voltage to the compressor contacts for testing, strictly monitor the turn-on time. Do not keep the power supplied for more than 3-5 seconds if the motor does not start. Prolonged supply of current without rotation of the rotor is guaranteed to burn the winding.
Analysis of pressure and tightness of the system
If the electrical part is in order, the motor starts, but there is no cold, the problem may be in the mechanical part or freon leakage. For accurate diagnosis of pressure it is necessary pressure manifold. It is connected to a process fitting (often sealed) on the compressor housing.
With a working system, the suction pressure should be negative (vacuum), and the discharge pressure should be high. If the compressor pumps but the pressure does not increase, there may be a clogged capillary tube or a refrigerant leak. In such cases, the motor runs empty, overheats, but does not perform its function.
| Parameter | Normal value | Fault symptom |
|---|---|---|
| Winding resistance | 10–30 Ohm | 0 Ohm (short circuit) or ∞ (Open) |
| Breakdown to the body | ∞ (Infinity) | Any readings resistance |
| Current consumption | Indicated on the nameplate (±10%) | Significantly higher than normal |
| Case temperature | Hot, but tolerable | Red hot or cold |
Checking for leaks is also important. If there are microcracks in the system, freon evaporates and the compressor begins to circulate air. You can determine a leak using a soap solution, applying it to the pipe connections, or using a special leak detector. Refrigerant itself has no odor, so visual or instrumental methods are indispensable here.
Specifics of diagnostics of inverter compressors
Modern refrigerators, such as Samsung or Boschare often equipped with inverter compressors. Their verification is fundamentally different from the diagnosis of conventional linear models. Such motors do not have a classic starting relay, but are controlled by an electronic unit that converts the current.
You can ring the windings of the inverter motor with a multimeter, but the results will be less informative, since the resistance there is very low. The main problem with inverters is the difficulty of diagnostics without a special tester that simulates the operation of the control board. A regular “continuity test” can only exclude an obvious break or breakdown in the housing.
If the inverter refrigerator displays an error on the display or the indicator blinks, first check the control board. Power surges in the network often damage the electronics, while the mechanical unit itself remains intact. Repair of such systems requires high qualifications and the availability of original spare parts.
When a compressor replacement is necessary
Replacing a motor is a complex and expensive process that requires evacuation of the system and refilling with freon. If the diagnostics showed a break in the windings, a breakdown in the housing or jamming of the mechanism, replacement cannot be avoided. In some cases, the cost of repairs with replacement of the compressor can be up to 70% of the price of a new refrigerator.
When deciding to replace, consider the age of the equipment. If the refrigerator is more than 10 years old, replacing the “heart” may not be economically feasible. Old thermal insulation materials could lose their properties, and other components could wear out. In such a situation, it is easier to purchase a new model with a modern energy efficiency class.
⚠️ Attention: Independent replacement of the compressor without a vacuum pump and scales for refilling freon is prohibited. The air and moisture remaining in the system will lead to blockage of the capillary and failure of the new motor within a few days.
However, if the equipment is new or premium, replacing the compressor will extend its life for many years. It is important to choose a model with similar characteristics: power, refrigerant and type of fastening. Using an unsuitable analogue will lead to incorrect operation of the cooling system.
Is it possible to check a compressor without a multimeter?
Completely check without devices are not allowed. One can only indirectly judge by sound, temperature and the presence of vibration. However, the “poke method” with direct voltage supply is dangerous and does not provide accurate data on the condition of the windings.
Why is the compressor hot, but the refrigerator does not freeze?
This indicates that the motor is running, but the refrigerant is not circulating. Reasons: freon leak, clogged capillary tube or faulty valves inside the compressor.
How much does it cost to replace a compressor?
The price consists of the cost of the unit itself and the work of the technician with consumables (freon, solder, filter). On average, this amounts to a significant amount, comparable to the purchase of used equipment in good condition.
Does a faulty compressor hum?
Yes, the nature of the hum changes. There is a metallic knocking, clanging or intermittent humming sound. A quiet, uniform hum is a sign of proper operation.