Faced with a situation where your refrigerator stopped freezing, and a puddle formed inside or, conversely, all products became covered with ice, many immediately panicking. However, the cause is not always the failure of the very heart of the unit - the motor. Often the problem lies in simpler elements, such as a thermostat or start relay, which can be replaced yourself without calling a technician. It is important not to rush to conclusions and conduct an initial diagnosis in order to understand the scale of the disaster and the economic feasibility of restoration.
A compressor is a complex electromechanical unit that is responsible for circulating refrigerant through the system. If it stops working, the cooling cycle is disrupted and the temperature in the chambers begins to rise to room temperature. Inverter models and classic units with conventional engines may behave differently if they break down, but the basic diagnostic principles remain similar. In this article, we will look at how to determine the malfunction, whether it is worth repairing the old motor or whether it needs to be replaced, and how to carry out the replacement safely.
Main signs of a compressor malfunction
The first alarm signal is a change in the characteristic sound background of the operation of a household appliance. If you hear the engine struggling to start, making a loud clicking noise, humming for a few seconds and then stopping, this is a sure sign of a problem. This mode of operation is called “cyclic starting”, and it is extremely harmful for the windings of the electric motor, since starting currents can reach enormous values, causing overheating.
In some cases, the motor can operate continuously without turning off, but still not create the necessary cold. This often indicates a loss of performance, a freon leak or a blockage of the capillary tube, but it may also indicate mechanical wear of the piston group. Double-circuit systems cooling if one of the compressors breaks down (in twin-engine models) will only cool one chamber, which is also a diagnostic sign.
⚠️ Attention: If, when trying to start, you hear a crackling sound, see sparks or smell burnt wiring, immediately disconnect the device from the power supply. Further experiments may lead to a short circuit or fire.
It is also worth paying attention to the temperature of the motor housing itself. If it heats up to such an extent that it is impossible to touch it, this may indicate an interturn short circuit in the windings or jamming of the mechanism. Normally, the unit should be warm, but not scalding.
Diagnostics: checking the starting relay and windings
Before sinning on the motor itself, it is necessary to rule out a malfunction of the starting relay. This small element is responsible for supplying a starting pulse and turning off the starting winding after gaining speed. If the relay is stuck or burnt out, the engine will not be able to start, although it may be completely fine on its own. To check the relay, you need to remove it and shake it: if a ringing is heard inside, it means that the core has broken off and the part requires replacement.
Next, you should check the integrity of the electric motor windings using a multimeter. Switch the device to resistance measurement mode (Ohm) and ring the contacts on the block. You need to find the common wire and measure the resistance between it and the working one, as well as between the common and start contacts. Normal readings vary depending on the power, but usually range from 10 to 40 ohms for the operating winding and slightly higher for the starting winding.
If the multimeter shows infinity (open) or zero (short circuit), then the windings are burned out. It is also critically important to check the resistance between any contact and the copper tube or motor housing. Breakdown to the housing - this is a dangerous malfunction that not only disables the equipment, but also creates a risk of electric shock when touching the metal parts of the refrigerator.
Preparation for replacing the compressor
If diagnostics have confirmed that the motor is faulty, it is necessary to prepare the workplace and tools. You will need a new compressor, which in terms of its characteristics (power, refrigerant, oil type) completely corresponds to the old one. An incorrectly selected model may quickly fail or not provide the required temperature. You will also need a pipe cutter, a torch with solder, a vacuum pump and a pressure gauge station for refilling with freon.
Replacement work is carried out only after the unit is completely disconnected from the network and the chambers are defrosted. It is advisable to take the refrigerator out into the fresh air or into a well-ventilated area, since residual gas may be released during dismantling, and soldering requires an open flame. Refrigerants R134a and R600a (isobutane) have different properties, and R600a is also explosive, which requires special care.
During the preparation process, it is necessary to drain the old compressor oil from the faulty unit in order to assess its condition. If the oil is black, has metal shavings, or has a burning smell, this confirms the mechanical destruction of the components. Clear amber-colored oil may indicate an electrical problem or simply normal wear and tear.
Step-by-step instructions for dismantling an old motor
The first step is to carefully cut with wire cutters or saw through the copper tubes connecting the compressor to the condenser and evaporator. This must be done carefully so as not to damage adjacent elements of the system. After disconnecting the tubes, the motor will be supported only by the mounting bolts or studs, which need to be unscrewed, having first secured the unit so that it does not fall.
Then remove the starting relay and thermal protection from the contact group of the new motor (if they are included) or carefully transfer them from the old one if they are in good condition. Note the orientation of the relay: it has an arrow or "Top" marking on it indicating the top position. Incorrect installation will lead to instant combustion of the part when turned on.
⚠️ Attention: When working with open fire, follow fire safety rules. Do not direct the burner flame at the plastic parts of the refrigerator and make sure that there are no flammable materials in the work area.
Install the new compressor in its original place, securing it with bolts. Do not over-tighten the fasteners to avoid damaging the rubber vibration isolators, but make sure the motor sits firmly and does not wobble. Now you can proceed to soldering the tubes, which requires certain skills in working with soft solder and a gas torch.
☑️ Tools for replacement
Soldering tubes and evacuating the system
Soldering copper connections is the most critical stage on which the tightness of the entire system depends. The tubes need to be cleaned to a shine, put on them and on the compressor fittings, and then heat the joint with a torch, introducing a rod of solder. A high-quality connection should be smooth, without sagging or cracks. It is important not to overheat the soldering area, so as not to melt the tube itself, especially if it is thin-walled.
After installing the motor and soldering all connections, it is necessary to evacuate the system. This is done to remove moisture and air, which, when mixed with refrigerant and oil, form aggressive acids that destroy the system from the inside. The vacuum pump is connected through the service connection, and pumping lasts at least 15-20 minutes until a pressure of about -1 bar is reached.
If you skip this step, the remaining moisture will freeze in the capillary tube, forming an ice plug, and the refrigerator will stop freezing again after a few hours of operation. Vacuuming also allows you to check the system for major leaks: if the pressure starts to rise when the pump is turned off, it means that somewhere there is a fistula that needs to be found and sealed.
Why can’t you refill without a vacuum?
There is always air containing moisture left in the system. When the refrigerator operates, moisture turns into ice in the narrow channel of the capillary, blocking the freon flow. In addition, oxygen in the air oxidizes the oil, turning it into acid, which corrodes the metal from the inside.
Refilling with refrigerant and checking operation
Refilling is carried out strictly according to the weight indicated on the technical sticker inside the refrigerator compartment or in the device passport. The use of a cylinder with a scale or a graduated cylinder is mandatory, since “filling by eye” by pressure often leads to errors. An excess of freon increases the pressure in the system and the load on the engine, and a deficiency does not provide the required cold.
After refueling, turn on the refrigerator and let it run for 15-20 minutes. Check the uniform heating of the condenser (grid at the back) and the operation of the evaporator inside the chamber. The pressure on the pressure gauge should stabilize within the operating limits specific to the specific type of refrigerant. If all parameters are normal, the service pipe is cut and sealed.
The final stage is to install the protective casing and return the refrigerator to the place of operation. During the first day, it is recommended to monitor the temperature in the chambers and the operation of the motor to make sure there are no extraneous noises or vibrations. A correctly installed unit should operate cyclically, turning on and off according to the thermostat readings.
Table of common faults
To quickly navigate the symptoms and possible causes of breakdowns, use the following table. It will help narrow down the search for the problem before starting an in-depth diagnosis.
| Symptom | Probable cause | Solution method |
|---|---|---|
| Click and silence | Faulty starting relay or winding break | Replacement of the relay, motor continuity |
| Buzzes, but does not start | Stuck piston group | Attempt to start through the starter, replacement |
| Works without stopping | Freon leak or compressor wear | Searching for leaks, refilling or replacing |
| Strong vibration and noise | Destruction of the suspension or shock absorbers | Replacing rubber elements, straightening tubes |
| The machine knocks out in the panel | Breakdown of the winding on the body | Urgent replacement of the compressor |
Frequently asked questions (FAQ)
Is it possible to repair an old compressor, or just replace it?
In a domestic environment, repairing the compressor itself (opening the housing, replacing valves or pistons) is practically impossible and inappropriate. The cases are sealed at the factory, and their hermetically sealed restoration requires industrial equipment. Usually, the unit is completely replaced with a new or refurbished analogue.
How long does it take to replace a compressor?
For an experienced technician with a full set of equipment, the process takes from 1 to 2 hours, including evacuation and refilling. An independent replacement without experience can take half a day or more, especially if difficulties arise with soldering or finding leaks.
Why does the refrigerator freeze less quickly after replacing the compressor?
This may be a consequence of poor-quality vacuuming (moisture remains), incorrect dosage of freon, or the use of an unsuitable motor power. It is also worth checking the cleanliness of the condenser and the operation of the fan, if any.
Is it dangerous to change the compressor yourself?
Yes, it is fraught with risks. Working with open fire, high voltage electricity and chemicals (freon, oil) requires compliance with safety precautions. In addition, incorrect refilling can lead to a refrigerant explosion (in the case of R600a) or failure of a new part.