The situation when the refrigerator stops cooling, and the motor is silent or makes only a short hum, takes any owner by surprise. Most often, the problem lies in the fact that the compressor is jammedand it cannot overcome the refrigerant pressure or the friction of the piston group. Before calling a technician, you should try to understand the reasons for the blockage, since in many cases the unit can be revived yourself by replacing failed components.
However, it is worth understanding that jammed piston inside a sealed casing is not always a death sentence, but often requires specific actions. If the motor hums for a couple of seconds and clicks when it switches off, then the thermal release has tripped due to overload. In this case, starting is possible, but only after eliminating the root cause of the blockage or replacing the trigger mechanism.
Do not immediately disassemble the unit completely. First, you need to carry out a primary diagnosis, which will help you understand whether the electric motor itself is alive or the problem lies in the starting system. Electrical circuit The refrigerator is designed in such a way that it protects the motor from combustion by breaking the contact at a critical current. Your task is to bypass the temporary protection and check the mechanical part.
⚠️ Attention: Any work on diagnosing the electrical part of the refrigerator should be carried out only with the power completely disconnected from the network. Residual voltage in capacitors can be dangerous.
Primary diagnosis and visual inspection
The first step will be visual inspection the rear of the unit. Remove the protective casing covering the compressor area and carefully examine the condition of the wires and the motor itself. If you see blackened insulation or smell a burning smell, then a breakdown of the winding has probably occurred, and starting such an engine is already useless and dangerous.
Pay attention to the temperature of the compressor housing. If it is hot, allow it to cool completely before trying to turn it on again. Thermal relay it could trip due to overheating, and until the bimetallic strip cools down, the circuit will not close. In some cases, it is enough to simply wait 30-40 minutes for the unit to start working again.
Check the integrity of the supply cables. It often happens that vibration during operation weakens the contacts in the terminal block. Oxidized or dangling wires create high contact resistance, which prevents sufficient current from flowing to the windings to create a starting torque.
- 🔍 Check the condition of the power cord for kinks and damage to the insulation.
- 🌡️ Touch the motor housing: it should be warm, but not hot.
- 🔌 Inspect the plug and socket: sometimes the problem is trivial and lies in poor contact in the wall.
If there are no external signs of a malfunction, we proceed to a deeper check of the electrical part. It is important to rule out problems with the wiring at home by connecting another powerful device, such as a hair dryer or iron, to the same outlet to make sure there is voltage.
Checking and replacing the starting relay
The most common reason that the engine does not start is a malfunction starting relay. This small plastic block, placed over the contacts of the compressor, is responsible for supplying voltage to the starting winding at the moment of start. If its contacts are burnt or the mechanical part is jammed, the motor will hum but not spin.
Remove the relay by carefully disconnecting the wires (after photographing the connection diagram). Older models use relays with a posistor, while more modern ones use an electromagnetic drive. Inside, you may find melted plastic or carbon deposits on the contacts, which indicates the need for replacement.
How to check a relay with a multimeter?
To check a posistor relay, ring its contacts. When cold, the resistance should be low (tens of ohms). If the device shows infinity or zero, the element is faulty. For electromagnetic relays, it is important to check the stroke of the coil and the condition of the contacts.
Replacing a relay is a simple process, but requires care. The new element must fully match the markings of the old one. Even a slight difference in characteristics can cause starting winding to burn out the next time you try to start.
- 🛠️ Carefully remove the old relay by pulling it down and wiggling it slightly.
- 📸 Take a photo connecting the wires before removing, so as not to reverse the polarity.
- 🧹 Clean the contacts on the compressor from oxides before installing a new part.
After installing the new relay, try turning on the refrigerator. If the engine starts and hums smoothly, the problem is solved. If the situation repeats itself, then the problem is not in the relay, and you need to look for the cause deeper, perhaps in the engine itself.
Diagnostics of electric motor windings
If the starting relay is working properly, the next step is to check the integrity of the windings of the compressor itself. To do this you will need multimeter. There are usually three contacts on the motor body: common, starting and working. It is necessary to ring them together and on the body.
In normal condition, the resistance between the common and working contacts, as well as between the common and starting contacts, should be in the range from 10 to 50 Ohms (depending on the model). The sum of these two resistances should equal the resistance between the start and run contacts. If the device shows infinity, the winding is broken; if zero, there is a short circuit.
Pay special attention to checking for breakdown of mass. Press one multimeter probe to any contact, and the second to a cleaned area on the compressor housing (where there is no paint). The device should show infinity. Any resistance value indicates that Insulation is broken, and such a motor cannot be operated.
| Check parameter | Normal value | Failure sign |
|---|---|---|
| Starting winding resistance | 20-40 Ohm | Infinity (break) or 0 (short circuit) |
| Working winding resistance | 10-25 Ohm | Significant deviation from the norm |
| Case resistance | Infinity | Any value (insulation breakdown) |
| Current consumption at startup | Up to 1.5 A (working) | Sharp jump and departure to cutoff |
If the diagnostics showed that the windings are intact, but the engine still does not start, there may be a problem in the mechanical part or the refrigerant circulation system. In this case, simple methods may not help.
Methods for forced motor starting
There is a method that allows you to start the engine bypassing the standard relay in order to check its mechanical ability to rotate. For this, a direct connection circuit to the working and starting windings is used. This method allows you to understand whether the piston is jammed or there is a problem in the electronics.
You will need a piece of wire with a plug and a button (or simply closing the contacts manually for a split second). Connect one wire to the common terminal, the second to the working terminal. The third wire (with the button) is briefly connected to the start terminal. When power is applied to the working winding and a short pulse to the starting winding, a serviceable motor should twitch and start.
Connection diagram:Phase (L) -> Button -> Starting winding
Zero (N) -> General winding
The working winding is connected in parallel through a capacitor (if required) or directly at the time of start.
Be careful: there is no protection with this connection. If the motor is jammed, the current will increase instantly, the wires may begin to melt, and the motor will burn out. Keep your finger on the button for no more than 1-2 seconds. If the motor does not start, do not hold the button longer.
- ⚡ Use wires with a cross-section of at least 1.5 mm² to avoid overheating.
- ⏱️ The duration of the starting pulse should not exceed 2 seconds.
- 🧤 Work in dielectric gloves and use tools with insulated handles.
⚠️ Attention: This method is diagnostic and emergency. Continuous operation of the refrigerator without a standard starting relay and protective devices is prohibited, as this can lead to a fire or failure of the compressor.
If after giving a pulse there is a dull knock, but there is no rotation, most likely the piston group is really jammed. In this case, it will be necessary to take more radical measures or replace the unit.
Mechanical wedging and external influences
Sometimes the engine does not start because the oil has thickened or the piston has become stuck to the cylinder after a long period of inactivity. In such cases, it can help mechanical impact. You can gently tap the compressor with a rubber mallet or the wooden handle of a hammer to move the jammed parts out of place.
Another method is to heat the lower part of the compressor housing. Thermal expansion of the metal can increase the clearances and release a stuck piston. Use a hair dryer, heating the body evenly for 5-10 minutes. The temperature should not exceed 100-120 degrees so as not to damage the varnish coating of the windings.
There is also a “swinging” method. They try to start the motor in the opposite direction or with short-term high-power impulses in order to turn the shaft. However, this method requires special equipment and skills, since you can easily break through the winding.
If none of the methods helped, and the shaft does not rotate even under load, this means irreversible changes in the mechanics: scuffing on the cylinders, destruction of the connecting rod or valves. In this case, repairs are not economically feasible.
- 🔨 Tapping should be moderate so as not to deform the tubes.
- 🔥 When heating, make sure that the plastic elements nearby do not melt.
- 🔄 The rocking method is effective only in 30% of cases and requires experience.
Replacement of the compressor: when repair is impossible
If the diagnostics showed a break in the windings, a breakdown in the housing or a mechanical jam that could not be eliminated, the only option left is compressor replacement. This is a complex procedure that requires a vacuum pump, a pressure gauge station and skills in working with the refrigeration circuit.
The new motor must be similar to the old one in terms of performance (m³/hour), refrigerant (R134a, R600a) and oil type. Installing the wrong compressor will result in the refrigerator operating inefficiently or quickly breaking down. It is also important to replace the filter drier, since the old one is already saturated with moisture.
☑️ Checklist before replacing the compressor
The replacement process includes bleeding off the remaining freon, soldering the old motor, soldering the new one, evacuation of the system and charging with refrigerant. Without evacuation, moisture will remain in the system, which during operation will freeze in the capillary tube and again block the operation.
⚠️ Attention: Replacing the compressor yourself without special equipment is impossible. An attempt to simply re-solder the tubes without evacuation will lead to rapid breakdown of the new motor.
The cost of a new compressor and the work to install it often makes up a significant part of the price of a new refrigerator. Therefore, before starting work, it makes sense to evaluate the economic feasibility of repairs.
Is it possible to restore a seized compressor forever?
In rare cases, if the seizure is caused by oil thickening or oxidation, prolonged heating and rocking can help. However, the service life of such a motor will be significantly reduced, and a second wedge is possible at any time. It is safer to replace the unit.
Why does it hum, but does not start?
This is a classic sign that the starting winding receives current, but the starting torque is not enough to turn the shaft. Reasons: faulty starting relay, low voltage in the network, turn-to-turn short circuit in the windings or mechanical piston wedge.
Is it dangerous to open the compressor yourself?
Yes, it is extremely dangerous. There is compressed gas inside, which can ignite upon contact with air (if there is a propane-butane mixture). In addition, there are oil vapors that are dangerous to breathe. It is strictly not recommended to open the sealed casing at home.
How much does a new compressor cost?
The price depends on the brand and power. For household refrigerators, the cost of a new motor varies from 3,000 to 8,000 rubles, excluding the cost of work and materials for refilling.
What to do if, after replacing the relay, the refrigerator does not turn on again?
You need to check the integrity of the windings with a multimeter. If everything is in order with the windings, there may be a problem in the wiring, thermostat or control unit (for models with electronics), which do not send a signal to start.