A sudden stop in the operation of refrigeration equipment often becomes an unpleasant surprise, causing you to panic due to the risk of food spoilage. If the unit has stopped cooling, but the light is on inside and there are no obvious errors on the panel, the first suspicion usually falls on the main node of the system - compressor. It is he who is responsible for the circulation of the refrigerant, and its failure paralyzes the entire operation of the device.
Before calling a technician or buying a new refrigerator, it makes sense to conduct an initial diagnosis. This will allow you to understand the scale of the problem: whether a complex replacement of the unit is required or whether it is enough to replace an inexpensive starting element. A competent checking the compressor can save a significant amount of money and time waiting for service.
In this material we will analyze a step-by-step algorithm of actions, the necessary tools and methods for measuring electrical parameters. You will learn to distinguish a mechanical knock from an electrical breakdown and understand when do-it-yourself repair still makes sense.
Primary diagnostics and visual inspection
You should start any work only after completely disconnecting the device from the electrical network. This is a basic rule, which, if ignored, can result in serious injury. First, move the refrigerator away from the wall to provide access to the rear of the case, where the motor-compressor is located. electrical safety, which, if ignored, could result in serious injury. First, move the refrigerator away from the wall to provide access to the rear of the cabinet where the motor-compressor is located.
Carefully inspect the back wall for external damage. You should not be interested in scratches on the paint, or the condition of the pipes and the motor casing itself. If you see oily spots, swelling or burning marks, this may indicate a freon breakdown or leak.
⚠️ Attention: If you find obvious traces of oil around the compressor or on the floor underneath it, this often indicates a depressurization of the system. In this case, simply replacing the motor without vacuuming and refueling the system will not help.
Turn on the refrigerator and listen. A working unit emits a steady hum that periodically subsides. If you hear clicks, a hum that ends abruptly, or complete silence when the lamp is on, these are signs of a malfunction of the electrical part or blade piston group.
Check the temperature conditions. If the motor hums constantly without turning off, and the temperature in the chambers does not drop below room temperature, there may be a loss of performance or a refrigerant leak. In this case, the motor itself may be in good working order, but run idle.
Necessary tools for testing
For high-quality diagnostics, you will need a minimum set of tools, which a home mechanic often already has. The main device will be multimeter (tester), which allows you to measure the resistance of the windings and check the integrity of the circuit. Without it, diagnostics will be only a superficial guess.
You will also need screwdrivers (phillips and flathead) to remove the protective casing and terminal box. Pliers for careful removal of wires and electrical tape for marking or temporarily insulating contacts will not be superfluous. To check the starting relay, a container of water is sometimes required if there is no special tester.
If you plan to carry out a more in-depth test, including measuring current consumption, you will need current clamps. However, for the initial diagnosis of the integrity of the windings and the starting device, an ordinary household tester is sufficient.
- 🔧 Multimeter (required with the function of measuring Ohm resistance)
- 🔧 Set of screwdrivers for dismantling the casing
- 🔧 Pliers or pliers
- 🔧 Electrical tape and marker for marking wires
Dismantling and access to the electrical part
After the refrigerator is unplugged for at least 15-20 minutes (to discharge the capacitors and stabilize the pressure), you can begin disassembling. Remove the rear metal or plastic panel covering the compressor compartment. It is usually secured with several screws or latches.
You will see a black barrel-shaped element - this is the compressor. A plastic box fits on one or both sides of it - a starting relay and a protective thermal relay. This is where the cause of failure most often lies.
Carefully remove the terminal block with the compressor contacts. It may be a tight fit, so rock it slightly from side to side, avoiding sudden jerks to avoid breaking the wires. Before removal, be sure to photograph or sketch the connection diagram, since it is very easy to mix up the contacts during assembly.
☑️ Preparation for diagnostics
Now you have access to three contacts on the motor housing. Two of them are windings (starting and working), and the third is the common output. It is these that we will “call” with a multimeter.
Checking the starting and thermal relay
Often motor-compressor itself is completely working, and the problem lies in the starting relay. This device is responsible for supplying an impulse to the starting winding to start the engine. If the relay does not operate, the motor only hums, but cannot start.
Remove the relay from the housing. Visually inspect it for cracks, melting or a burning smell. If you hear a ringing sound inside when you shake it (like a loose contact), the part definitely needs to be replaced. For electrical testing, use a multimeter in resistance measurement mode.
Ring the relay contacts. The resistance should be close to zero or several ohms, depending on the type of device. If the device shows one or infinity, then the circuit is broken and the relay needs to be changed. This is a consumable item that is inexpensive.
⚠️ Attention: The thermal relay (overheating protection) may also fail. Check its contacts - when cold they should ring short. If the circuit is open even on a cold engine, the protection is faulty.
There is a simple way to check the operation of the relay without instruments, but it requires caution. You can apply voltage directly to the windings, bypassing the relay, but you should only do this if you are confident in your abilities and understand the risks of a short circuit.
Diagnostics of compressor windings with a multimeter
The most important stage is checking the integrity of the windings of the engine itself. There are usually three contacts on the compressor housing, often covered with a cover. After removing the relay, you see three pins forming a triangle.
Switch the multimeter to resistance measurement mode (200 Ohm or 2 kOhm limit). Call pairs of contacts sequentially. For a working single-phase compressor, you should get three resistance values: between the common and working windings, between the common and starting windings, and between the working and starting windings.
The sum of the resistances of the two smaller values should be equal to the third, largest value. For example, if between contacts A-B there are 20 Ohms, B-C 50 Ohms, then between A-C there should be about 70 Ohms. Any deviation or “infinity” reading indicates a break.
Table of normal resistance values
Values may vary depending on the power of the motor. For low-power refrigerators (up to 150 W), the resistance of the working winding is 10-25 Ohms, the starting winding is 20-40 Ohms. For powerful units the values may be lower. The main thing is that there is no short circuit to the case.
It is critically important to check whether there is breakdown to the housing. Touch one multimeter probe to any contact, and the other to a cleaned area on the compressor housing (where there is no paint). The device should show infinity. If there is at least some resistance, the motor is faulty and dangerous to life.
Below is a table with approximate resistance values for different types of compressors, so that you have something to compare your measurements with.
| Winding type | Normal resistance (Ohm) | Malfunction symptom |
|---|---|---|
| Working (Main) | 10 – 35 Ohm | Open (∞) or short circuit (0 Ohm) |
| Starting | 20 - 60 Ohm | Open (∞) or short circuit (0 Ohm) |
| Between windings | Sum of values | Discrepancy with the sum |
| On the body | ∞ (Infinity) | Any value (Breakdown) |
Mechanical check and start directly
If the electrical part is normal (the windings are intact, the relay is working), but the refrigerator does not turn on, the compressor may be jammed. This is a mechanical malfunction when the piston group loses mobility due to production or lack of oil.
There is a direct starting method, bypassing the start relay. To do this, a voltage of 220V is supplied to the compressor contacts. However, this must be done extremely carefully and briefly. If the motor is mechanically working, it should attempt to start with a characteristic sound.
If, when voltage is applied, a loud hum is heard, turning into a knock, and knocks out the circuit breakers in the panel - most likely there is an engine problem. Attempts to wedge it with hammer blows or increasing tension rarely give lasting results. wedge engine. Attempts to wedge it with hammer blows or increasing tension rarely produce lasting results.
It is also worth checking the valve system. If the compressor pumps, but weakly, there may be a problem with the valves. This is checked by the outlet pressure, which requires connecting a pressure gauge station. If there is no pressure at all while the engine is running, the compressor has “died” mechanically.
⚠️ Attention: Starting the compressor directly without standard protection (thermal relay) is dangerous. Hold the wire only by the insulation; the duration of switching on should not exceed 3-5 seconds, so as not to burn the windings.
Common mistakes in diagnostics
Beginners often make mistakes that lead to false conclusions. One of them is a “hearing” test without tools. The hum can be caused not only by a broken motor, but also by improper installation of the refrigerator when it vibrates against the wall.
Another mistake is ignoring the condition of the wiring. Before using the compressor, make sure that the voltage reaches the outlet and the device itself. Often the problem lies in a burnt-out surge protector or a broken wire.
Don't forget about the thermostat. If it is faulty and does not close the circuit, the compressor simply will not receive the start command. Ring the thermostat contacts - in the “maximum cold” position they should ring.
Remember that modern inverter compressors are diagnosed differently. They cannot be checked by the usual ringing of the windings or run directly from a 220V network. They require a special tester or replacement of the control module.
Frequently asked questions (FAQ)
Is it possible to replace the compressor yourself?
Theoretically, yes, but this requires special equipment: a vacuum pump, a pressure gauge station and a supply of freon. You can’t just re-solder the tubes and fill in gas “by eye” - the system will quickly fail. A skilled technician is required.
How long does a compressor last in a refrigerator?
The average service life of a modern compressor is 10-15 years. However, if used incorrectly (frequent defrosting with a knife, installation near a battery, power surges), it can fail much earlier.
Why is the compressor hot to the touch?
In operating condition, the compressor heats up to 60-90 degrees Celsius, this is normal. But if it is so hot that it is impossible to touch it, and the refrigerator does not freeze, this is a sign of overload or freon leakage.
What is cheaper: repair or a new refrigerator?
Replacing a compressor with freon charging costs approximately 40-60% of the cost of a new refrigerator. If the unit is old, it is often more profitable to buy new equipment with a guarantee and energy efficiency class A+.