The situation when the refrigerator stops cooling, and the compressor is silent or makes only a quiet click, often confuses the home craftsman. The first suspicious element is the starting relay, which is responsible for starting the engine, but inexperienced users may mistakenly replace a working part, leaving the problem unresolved. To avoid unnecessary expenses and accurately diagnose a malfunction, you need to know how to check the operation of a refrigerator compressor without a relay by excluding this auxiliary element from the circuit.
Direct starting of the motor allows you to understand whether it is alive unit or whether the problem lies deeper, for example, in broken windings or mechanical jamming of the piston group. However, this procedure requires strict adherence to safety precautions, since you are working with high voltage and exposed electrical contacts. In this article we will analyze in detail all stages of diagnostics, from preparing tools to interpreting the results of measurements with a multimeter.
It is worth immediately noting that testing without a relay is a temporary diagnostic measure, and not a method of permanent operation. Starting device protects the windings from overheating and ensures the correct phase shift to create rotating moment. If, after a successful direct start, the refrigerator does not work in normal mode with a new relay installed, then the reason lies in the motor itself or the refrigerant circulation system.
Theoretical basis of the operation of the starting mechanism
To understand the diagnostic process, it is necessary to briefly consider the principle of operation of the standard single-phase switching circuit engine. The refrigerator compressor has two main windings: working and starting. The working winding creates the main magnetic field, and the starting winding is needed only at the moment of start to create torque, after which it must be turned off.
It is this switching function that is performed by the starting relay, which can be electromagnetic or posistor. In electromagnetic models, the current passing through the working winding creates a magnetic field that draws in the core and closes the contacts of the starting winding. Posistor relays operate on the principle of changing resistance when heated by current.
- 🔌 Electromagnetic relay - emits a characteristic click when turned on and off, often fails due to burning of the contacts.
- 🔥 Posistor - has no moving parts, but can lose its properties over time, ceasing to pass current to the starting winding.
- ⚡ Thermal relay - often combined with the starting winding and serves to protect against current overloads, breaking the circuit when overheated.
When you remove the relay from the circuit, you In effect, you take on the role of an automatic switch, applying voltage to the starting winding only for a short time. An error in the timing or connection sequence can lead to the motor humming without rotor rotation, which can lead to rapid overheating and insulation breakdown.
⚠️ Attention: Never leave voltage applied to the starting winding for more than 3-5 seconds without rotor rotation. This is guaranteed to lead to burnout of the starting winding or thermal breakdown of the insulation, after which the compressor can only be disposed of.
Why does it hum, but does not start?
If, when voltage is applied, the compressor hums loudly, but the shaft does not turn, this may indicate for jamming of a mechanical part or a critical voltage drop in the network. In some cases, a short-term supply of increased voltage helps, but this requires special equipment.
Necessary tools and precautions
Before proceeding with “surgical intervention” in the electrical circuit, it is necessary to prepare the workplace and tools. Safety comes first here, since mistakes can cost not only expensive equipment, but also the health of the technician. You will need a basic electrician's kit and some specific devices.
The main diagnostic device will be a multimeter capable of measuring resistance in the range of up to 2 kOhm and checking the integrity of the circuit. You will also need a screwdriver, pliers, insulating tape and, preferably, a pair of wires with alligator clips for easy connection to the contacts.
☑️ Checking readiness for diagnostics
It is important to ensure dry hands and the working surface. Humidity dramatically reduces the resistance of human skin, increasing the risk of electric shock. If you are performing diagnostics in a garage or basement, make sure there is good lighting so you can clearly see the pin markings.
Visual inspection and preparation of the compressor
The first diagnostic stage begins long before connecting the wires. You will need to remove the back panel of the refrigerator to gain access to the compressor. A visual inspection can immediately answer the question of whether it is worth spending time on further checks.
Carefully inspect the motor housing for swelling, traces of oil or soot. The presence of oily stains in the lower part of the unit often indicates depressurization of the system, which makes compressor repair economically impractical. Also check the condition of the contact group.
| External sign | Probable cause | Action |
|---|---|---|
| Rust on the body | High humidity, condensation | Clean, check tightness |
| Traces of oil | Rupture of pipeline or seal | Requires calling a technician with freon |
| Melted plastic relay | Short short circuit or overload | Replace the relay and check the current |
| Cracks in the tubes | Mechanical damage | Soldering and filling the system |
If the unit visually looks intact, it is necessary to remove the starting relay It is usually attached to three contacts extending from the compressor housing. Carefully remove it; you may have to remove the retaining clamp or frame. Do not use excessive force to avoid breaking off the contacts.
After removing the relay, wipe the contacts with a dry cloth. Oxides can distort resistance measurements. Make sure that the three pins coming out of the compressor are arranged in a triangle and have no visible damage.
Diagnostics of the windings with a multimeter
The most reliable method of initial testing is to test the windings with a tester. This procedure allows you to identify an open circuit or short circuit to the frame, which is a fatal defect. Switch the multimeter to resistance measurement mode (Ohm) to a limit of 2000 Ohm.
On the end of the compressor you will see three contacts. They are usually marked, but if the marking is erased, their purpose needs to be determined. The pair of contacts with the highest resistance are the ends of the starting and running windings connected in series. The third contact, located separately, is common.
- 📏 Resistance measurement —measure the resistance between each pair of contacts. The sum of the resistances of the starting and operating windings should be equal to the resistance between the outer contacts.
- 🚫 Checking for breakdown —place one probe on any contact, and press the second one to the cleaned area on the compressor body (where there is no paint). The device should show infinity.
- 🔄 Comparison of readings —the resistance of the working winding is usually lower (10-30 Ohms) than the starting winding (30-60 Ohms), although in some models Indesit or Ariston values may differ.
If the device shows one (infinity) on any of the windings, it means there is a break inside. It is impossible to restore such a winding at home. If the resistance is close to zero, this indicates an interturn short circuit, which also requires replacing the unit.
Method of direct engine starting
If the electrical tests are successful, you can proceed to the practical test - direct start. This method simulates the operation of a start relay by manually applying voltage to the start winding. To do this, you will need a piece of wire with a plug or two insulated wires.
The connection diagram is simple: the phase wire of the network is connected to one of the outermost contacts (usually common or working), and the zero wire is connected to the other outermost one. The third contact (starting) must be briefly closed with the phase wire. It is important not to mix up the contacts, otherwise the engine will hum but will not start.
⚠️ Attention: Make sure that there are no flammable objects nearby during the experiment. If the compressor is faulty, a spark may fly out of the contacts. Keep your face and hands away from the contact area.
Apply power. If the motor is silent, try briefly (for 1-2 seconds) to close the contact of the starting winding with the phase. If the compressor is working properly, you will hear a steady hum and feel vibration. The engine should start running smoothly.
After successful startup, let the motor run for a few seconds to evaluate the nature of the sound. A uniform hum without clanging or knocking indicates mechanical health. Do not forget to immediately turn off the power, since without a relay the compressor will not be able to operate for a long time and safely.
Analysis of results and typical errors
Interpretation of test results requires care. If the compressor starts but is humming louder than usual, this may indicate worn bearings or problems with the shock absorbers. If startup does not occur, despite serviceable windings, the piston is probably jammed.
A common mistake is incorrect identification of contacts. In compressors from different manufacturers, such as Atlant, Beko or Liebherr, the location of the contacts may differ. Always check the circuit diagram on the case or technical documentation if available.
Another common problem is using too thin starting wires. The starting current can be several times higher than the operating current, and thin wiring will simply burn out or create additional resistance, preventing the motor from spinning up.
- ❌ Timing error - holding the starting contact for too long leads to overheating of the winding.
- ❌ Poor contact - using twists instead of clamps "crocodile" creates the risk of sparking and loss of voltage.
- ❌ Ignoring the capacitor - some circuits have a starting capacitor, which also needs to be checked and connected correctly.
If after all the checks it turns out that the motor does not work, but electrically serviceable, “wedging” method. It involves applying increased voltage for a short time, but this method is dangerous and requires a special transformer, so it is not recommended at home.
Is it possible to leave the refrigerator working without a relay?
Absolutely not. Operating without a relay will result in the starting winding remaining constantly on, causing it to burn out instantly. The relay is necessary for normal cyclic operation.
What to do if the compressor is hot to the touch?
A hot compressor may indicate overload, jamming, or problems with heat transfer (dirty condenser). Let it cool completely before re-diagnosis.
How to distinguish compressor noise from fan noise?
Compressor noise is a low-frequency hum and vibration of the housing. Fan noise is a high-frequency whistle or crackling sound of the blades that stops when the fan stops.
Is it necessary to change the oil after checking?
During short-term diagnostics, an oil change is not required. However, if the compressor has been opened or worked for a long time with a breakdown, an oil change and evacuation of the system are required.
Why does the machine knock out when starting?
This is a sign of a short circuit in the windings or a wiring fault. Also, the reason may be too powerful a starting current when the rotor is jammed.