Refrigerator Has it stopped freezing, but all you can hear inside is a quiet hum or complete silence? In 90% of cases, the cause of the breakdown is compressor the heart of the entire refrigeration system. It is this unit that is responsible for the circulation of the refrigerant, and its failure leads to spoilage of products and the need for urgent repairs.
Before calling a technician or buying new equipment, it is worth conducting an initial diagnosis yourself. Often the problem lies not in a burnt-out motor, but in a breakdown start relay or broken wiring, which is easy to fix with your own hands. In this article, we will look at how to safely check the condition of the engine using a minimum set of tools.
Remember that any work with electrical appliances requires compliance with safety precautions. Before starting diagnostics, be sure to disconnect the refrigerator from the power supply by removing the plug from the socket. Ignoring this rule can lead to electric shock or damage to electronic control units.
Initial visual inspection and condition assessment
Start diagnostics with an external inspection of the rear of the unit, where the compressor compartment is located. Carefully inspect the motor housing for physical damage, dents or traces of soot. The presence of black soot or melted areas on the wires often indicates short circuit or overheating of the windings.
Pay attention to the temperature of the case. If you turn on the refrigerator, some time has passed, but the motor remains cold, this is a sign that it will not start. Conversely, if the compressor is heated to the point where it is impossible to touch it, but there is no cold, the piston group may have jammed. water hammer or jamming of the piston group.
Also check the integrity of the electrical connections. Oxidized contacts or broken wires can simulate engine failure. Make sure that the terminals are tightly in place and have no signs of corrosion.
Diagnostics of the starting relay and thermostat
Before “sinning” on the motor itself, it is necessary to rule out a malfunction of the starting relay. This small block is responsible for supplying a starting pulse to the motor winding. If the relay is faulty, the compressor may hum but not start, or click and turn off immediately.
To check, remove the relay from the compressor. Shake it near your ear: if a ringing or knocking sound is heard inside, it means that the internal contact group is damaged or the coil is loose. This is a sure sign that replacement is needed. Also inspect the contacts for the presence of carbon deposits.
How does the starting relay work?
When the refrigerator is turned on, the relay supplies increased voltage to the starting winding, helping the rotor to spin up. As soon as the engine picks up speed, the relay opens the starting winding circuit. If this mechanism jams, the motor cannot start.
Don't forget to check the thermostat. If it does not close the circuit when the temperature rises, the signal to start the compressor simply will not arrive. Close the thermostat contacts directly (temporarily) and see if the motor starts. If after this procedure the refrigerator started working, the problem was in the temperature sensor.
Often users confuse the symptoms of a breakdown of the relay and the motor itself. To avoid mistakes, use the following checklist for a quick assessment:
☑️ Check before disassembly
Checking the compressor with a multimeter for open and short circuit
The most accurate diagnostic method is to use multimeter. This device will allow you to measure the resistance of the windings and identify internal defects that are invisible to the eye. Switch the tester to resistance measurement mode (Ohm) to a limit of 200 Ohm.
Find the three contacts on the compressor (usually they are covered by the terminal block). You need to ring each pair of contacts between each other and each contact on the housing. Normal resistance readings depend on the model, but usually fall within the following ranges:
- 🔹 Starting winding: higher resistance, usually 20-40 Ohms.
- 🔹 Operating winding: lower resistance, usually 10-20 Ohms.
- 🔹 Total resistance (between the extreme contacts): the sum of the two previous values.
- 🔹 Resistance to the body: should be infinite (one on the screen).
If the multimeter shows one (infinity) between any two contacts of the windings, it means in the circuit break. Such a compressor cannot be repaired and requires replacement. If the device shows zero or a value close to zero, a break occurred interturn short circuit.
Pay special attention to checking for breakdown on the case. Touch one probe to any contact and the other to the bare metal of the compressor housing (where there is no paint). If the multimeter beeps or shows any resistance, it means that the insulation of the windings is broken. Operate such a unit is deadly!
Table of normal resistance values
For ease of diagnosis, we present average resistance values for various types of compressors. Remember that the exact data is always indicated in the manufacturer's technical documentation Atlant, Bosch or LG.
| Winding type | Normal resistance (Ohm) | Possible malfunction if deviation |
|---|---|---|
| Working (between contacts 1-2) | 10 – 25 Ohm | Open or inter-turn short circuit |
| Starting (between contacts 2-3) | 20 - 45 Ohm | Trigger coil burnt out |
| Common (between contacts 1-3) | Sum R1 + R2 | Circuit integrity violation |
| On the body (any contact - metal) | Infinity (∞) | Insulation breakdown, life-threatening |
It is important to understand that the resistance of the windings may vary slightly depending on the temperature of the motor. Cold a motor will show some values, and a warm one - others. However, the order of the numbers must be preserved: the resistance of the starting winding is always higher than the working one.
⚠️ Attention: If you find resistance on the case even of several Megaohms, do not take risks. Humidity inside the windings or microcracks in the varnish can lead to a sudden electric shock when touching the metal body of the refrigerator.
Direct start of the compressor (test without a relay)
If the electrical parameters are normal, but the engine does not start, you can try to start it directly, bypassing the standard starting relay. This method allows you to accurately determine whether the motor itself is alive. To do this, you will need a piece of wire with a plug and a button (or just carefully close the contacts).
The circuit is simple: the phase from the network must be applied to the common contact, and zero to the working one. The starting winding must be briefly short-circuited with the working winding (imitation of relay operation) at the moment of power supply. Be careful: the rotor can jerk with great force.
Connection diagram for the test:Network (L) -> Common contact (C)
Network (N) -> Working winding (R)
Short-term: Starting (S) <-> Working (R)
If, with a direct connection, the compressor starts and runs confidently, then the problem was in the starting relay or thermostat. If the motor only hums, jerks and knocks out the circuit breaker, then there is mechanical jam a piston group or a strong interturn short circuit.
Mechanical faults and jamming
The situation when the electrical part is working, the windings are intact, but the engine does not spin, often indicates a mechanical breakdown. Inside the sealed casing, cylinder scuffing, valve failure, or suspension destruction can occur.
A sign of a mechanical jam is often a characteristic metallic clanging or knocking sound when trying to start. The engine tries to turn over, but the pistons are stuck at a dead point. In some cases, the method of “swinging” by applying increased voltage helps, but doing this at home is highly not recommended.
- 🔸 Destruction of the valve group: the compressor works, but does not create pressure (no cold).
- 🔸 Breakage of the piston rod: a knock is heard, there is no pressure.
- 🔸 Bearing jamming: strong hum, overheating, knocking out plugs.
If you encounter a mechanical breakdown, repairing the compressor at home is impossible due to the need to open the sealed casing and the presence of special equipment for soldering and refilling with freon.
Often asked questions (FAQ)
Is it possible to repair a burnt-out compressor yourself?
No, the compressor is a sealed unit. To repair it, industrial equipment is required for cutting the body, welding, evacuation and charging with refrigerant. At home, you can only replace it with a new one.
Why is the compressor hot, but the refrigerator does not freeze?
This may indicate a loss of performance (wear of valves), a freon leak, or a malfunction of the defrost system. The engine is idling, trying to compensate for the lack of refrigerant or cycle disruption.
How much does it cost to replace a compressor?
The cost consists of the price of a new unit and the work of a technician to replace and refill with freon. On average, this ranges from 40% to 70% of the cost of a new refrigerator, so it is often more advisable to buy new equipment.
Is it dangerous to touch the compressor during operation?
Yes, the temperature of the housing of a working compressor can reach 90-100°C. In addition, if there is an insulation breakdown, a dangerous electrical potential may be present on the housing. Carry out all manipulations only with the power turned off.