A sudden stop of the refrigerator often takes you by surprise, especially when there are food supplies in the freezer. One of the first symptoms of a malfunction is the hum of a running compressor that does not go into normal cooling mode, or the complete lack of response of the unit when plugged into the network. In such cases, home craftsmen often consider the possibility of forcibly starting the engine in order to prevent damage to the motor itself.
Before deciding to take such a radical step, it is necessary to clearly understand the structure of the electrical circuit and the risks associated with interfering with the operation of high-voltage components. Start relay is a small but critical unit that ensures the engine starts and protects the windings from overloads. Its malfunction can simulate a compressor breakdown, creating the false impression of the need for an expensive replacement of the entire unit.
In this article we will analyze the technical aspects of temporarily closing contacts for diagnostic purposes, describe the differences between relay types and point out critical safety issues. Remember that any intervention in the electrical circuit requires precautions, since a voltage of 220 volts poses a real threat to life. The instructions are for informational purposes only and are intended for qualified users.
The design and principle of operation of the starting relay
To correctly carry out diagnostics, you need to understand exactly how it works starting system Starting relay performs the function of a switch that supplies voltage to the starting winding of the electric motor only at the moment of start. As soon as the rotor reaches the required speed, the relay automatically opens the starting winding circuit, and the engine continues to operate only on the main winding.
There are two main types of devices found in household refrigerators: electromagnetic (induction) and posistor (thermal). Electromagnetic models work by generating a magnetic field in a coil when current is applied, which draws in the core and closes the contacts. The posistor ones use the property of the material to sharply increase resistance when heated, actually breaking the circuit after warming up.
⚠️ Attention: An attempt to bridge the contacts without understanding the type of relay can lead to a short circuit or failure of the compressor windings. Make sure that you have identified the device correctly.
There is also often a thermal relay located inside the housing, which opens the circuit when the current or temperature of the motor housing critically increases. This is protection against insulation burning. When diagnosing, it is important not to damage this element, since its absence will leave the compressor defenseless against overheating. thermal release (thermal relay), which opens the circuit when the current or temperature of the motor housing critically increases. This is protection against insulation burning. When diagnosing, it is important not to damage this element, since its absence will leave the compressor defenseless against overheating.
Necessary tools and safety measures
Working with electrical appliances requires strict adherence to electrical safety rules. Before starting any manipulations, the refrigerator must be completely disconnected from the electrical network. It is not enough to simply turn off the device with the button; you must remove the plug from the socket. This will eliminate the risk of electric shock if you accidentally touch bare wires.
To carry out the work, you will need a minimum set of tools, which most home craftsmen can find. Pay special attention to insulating tools, since work will be carried out in close proximity to live parts. It is also recommended to use dielectric gloves if you are not sure that your hands and floor are dry.
- 🔧 Screwdrivers (phillips and flat) for removing the casing and dismantling the relay.
- 🔌 Multimeter or tester for checking the integrity of windings and contacts.
- 🧤 Dielectric gloves to protect your hands.
- 💡 Test lamp or socket with wires for checking voltage (optional).
If you plan to use the temporary short circuit method to check the motor, make sure that the work area is well lit and dry. Humidity can cause insulation breakdown or short circuit. In addition, prepare a container to collect possible oil residues if you have to remove the compressor or tilt the unit.
☑️ Safety check before work
Diagnostics of faults before intervention
Before moving on to radical measures, such as bridging the contacts, you need to make sure that the problem lies in the relay itself, and not in the compressor or wiring. Often the symptoms are similar: the engine hums but does not start, or it clicks and stops after a few seconds. This may indicate either a jammed piston group or a burnt-out relay.
The first step is a visual inspection. Remove the back cover of the refrigerator and get to the compressor. Carefully remove the plastic box in which the thermal protector is secured. Carefully inspect the device: the presence of burning, melted plastic, cracks or a characteristic burning smell clearly indicates the need for replacement. starting relay and thermal protector. Carefully inspect the device: the presence of burning, melted plastic, cracks or a characteristic burning smell clearly indicates the need for replacement.
Next, you should check the integrity of the motor windings using a multimeter. Switch the device to resistance measurement mode (Ohms). The compressor usually has three terminals: common (C), starting (S) and running (R). The resistance between the common and working terminals should be the smallest, between the common and starting terminals - average, and between the working and starting terminals - the sum of the previous two.
Table of normal resistance values
Values may vary depending on the power of the motor. For low-power compressors, the resistance can be 10-20 Ohms, for powerful ones - 3-5 Ohms. The main rule: the resistance between S and R must be equal to the sum of the resistances C-S and C-R. If the device shows infinity or zero, the winding is faulty.
If the resistance of the windings is normal, but the motor does not start, there is a high probability of a faulty trigger mechanism. It is also worth checking the thermal release: in a cold state it should “ring” (show zero or a value close to it). If the circuit is broken, the motor will not receive power at all.
Connection diagram and relay types
Understanding the connection diagram is necessary for correct diagnostics. Most modern refrigerators use posistor relays, which are structurally simpler than electromagnetic ones. They are a housing with a contact group and a posistor inside. Electromagnetic models have a moving core and coil, which makes them more sensitive to position (they only work in a certain position relative to the ground).
The relay contacts switch the starting winding circuit. When voltage is applied, current flows through the starting winding and the relay coil (or posistor). In an electromagnetic relay, the magnetic field pulls in the core, breaking the starting circuit. In a posistor, the current heats the crystal, its resistance increases, and the current drops to almost zero, which is equivalent to opening.
| Relay type | Principle of operation | Replacement features | Frequent faults |
|---|---|---|---|
| Electromagnetic | Retraction of the core by current | Orientation is important (top-bottom) | Contact sticking, coil burning |
| Posistor | Heating and resistance growth | Orientation is not important | Thermal posistor split, burnt contacts |
| Combined | Combination of thermal and starting | Replaced by a block entirely | Thermal release failure |
When removing the relay, pay attention to the markings of the wires and their location. Wires are usually color coded, but don't rely on color alone as manufacturers may change standards. It is best to take a photo of the original connection before disconnecting.
How to temporarily bypass the relay for testing
The method of temporarily closing contacts is used exclusively for diagnostics: to understand whether the compressor itself is alive. Important: leaving the refrigerator to operate without a working relay is strictly prohibited, since the starting winding will burn out in a matter of seconds or minutes.
To implement this method, you will need a piece of copper wire with stripped ends or a special diagnostic tool. The idea is to apply voltage to the starting winding only at the moment of start, simulating the operation of a working relay. This is done manually, so care and speed are required.
The action algorithm is as follows:
- ⚡ Disconnect the refrigerator from the network and remove the relay from the compressor contacts.
- 🔌 Connect the power directly to the working contacts of the compressor (common and working), bypassing relay.
- 🖐️ When you plug the plug into the socket, briefly touch the starting winding contact with the wire.
- 🔄 As soon as the motor starts and picks up speed (a steady hum will appear), immediately remove the wire from the starting contact.
⚠️ Attention: The contact time with the starting winding should not exceed 1-2 seconds. Holding it for a long time will lead to overheating and burning of the engine starting winding.
If after such a procedure the compressor starts and runs smoothly, then the problem was in the starting relay. If the motor hums, jerks, but does not start even with a manual pulse, or the circuit breaker knocks out, the compressor itself is most likely faulty (jamming or interturn short circuit).
Common mistakes and risks during self-repair
Independent repair of refrigerators involves a number of risks that enthusiasts often forget about. One of the most common mistakes is ignoring the state of the capacitor (if it is in the circuit) or the thermal relay. An attempt to start a motor with a faulty thermal release can lead to the fact that if the piston group is jammed, the engine will continue to operate until the windings are completely burned out, since the protection will not work.
Another mistake is the use of inappropriate materials for jumpers. Aluminum wire or copper wire that is too thin may not withstand the inrush current, which is 5-7 times the rated operating current. This may cause the insulation to melt and cause a fire. All temporary connections must be reliable and short-term.
It is also worth mentioning the risk of damage to the cold pipes. The compressor is a sealed unit. Careless handling of the tool or slipping of the screwdriver can pierce the thin wall of the tube or the motor housing itself. The release of freon into the atmosphere will not only stop the operation of the refrigerator, but will also require calling a technician to vacuum and refill the system, which will significantly increase the cost of repairs.
Do not forget that modern inverter compressors cannot be diagnosed using this method. They are controlled by complex electronics (inverter), and a direct supply of 220 volts to them will lead to instant failure. Direct connection to the network is only permissible for classic asynchronous motors.
Relay replacement and final assembly
After successful diagnostics, it becomes obvious that the relay must be replaced. Repairing an old device (cleaning contacts, washing) gives only a temporary effect, since the physical properties of the posistor or the parameters of the core spring have already been changed. Buying a new relay is the most reasonable decision.
When purchasing, pay attention not only to the appearance, but also to the markings. The relays must match the power of the compressor (indicated in watts or by refrigerator model). Universal relays exist, but it is better to choose an original or a high-quality analogue recommended by the manufacturer.
The process of installing a new element is simple:
- Place the new relay on the compressor pins until a characteristic click or stop is heard.
- Connect the wires in accordance with the previously taken photo or diagram.
- Make sure that the wires do not touch the hot parts of the compressor or each other.
- Attach the fixing bracket or bar, if provided by the design.
After assembly, turn on the refrigerator. Normal operation is characterized by a quiet start-up, no clicks and a gradual decrease in temperature in the chambers. If after 10-15 minutes of operation the compressor turns off and the temperature has dropped, the repair was successful.
Is it possible to leave the refrigerator operating without a relay if the contacts are tightly closed?
No, this is impossible. If you close the starting winding constantly, it will burn out in a few minutes, since it is not designed for long-term operation. The relay must open the circuit after starting.
Why does a new relay burn out immediately after installation?
There may be several reasons: a jammed compressor (the motor cannot turn over and the current increases), a malfunction in the electrical network (voltage surges) or a defect in the relay itself. It is also possible that a relay with inappropriate parameters was selected.
How much does it cost to replace a relay at a service center?
The cost consists of the price of the spare part and the work of the technician. On average in the market, this can range from 1,500 to 3,000 rubles, depending on the region and model of the refrigerator. Self-replacement saves the cost of work.
Is it dangerous to touch the compressor during operation?
Yes, it is dangerous. The housing of a running compressor heats up to 70-90 degrees Celsius, which can cause burns. In addition, there is a risk of electric shock if the insulation is damaged. Carry out all manipulations only with the device turned off.