The situation when the refrigerator suddenly stops cooling, and the compressor only hums or clicks, but does not start, is familiar to many owners of household appliances. Most often, the culprit of such a malfunction is starting relay, which is responsible for supplying the starting impulse to the engine. In emergency cases, when there is no replacement at hand, and the products require cooling, the question arises about the possibility of temporarily starting the motor bypassing this unit.
It is important to understand that starting relay is not just a switch, but a complex electromechanical element that protects the motor windings from overheating. Its absence or improper operation can lead to compressor wedge or even a fire. However, for short-term diagnostics or emergency switching on for several hours, there are proven methods that require strict adherence to safety precautions and an understanding of electrical circuits.
Before proceeding with any manipulations with the electrical wiring, it is necessary to completely de-energize the unit. Working with high voltage 220 volts requires caution, and you automatically perform any actions with the internal components of the refrigerator at your own peril and risk. In this article we will analyze the theoretical aspects of the operation of the circuit, diagnostic methods and methods for temporarily starting the motor.
The role of the starting relay in the operation of the compressor
A single-phase asynchronous motor installed in a refrigerator compressor is not capable of independently starting the rotation of the rotor. To create the initial torque, it needs a second winding, which is turned on only for the moment of start. It is this process that is responsible starting relay, which closes the circuit of the starting winding at the moment of switching on and opens it when the engine picks up operating speed.
In modern models, posistor relays are often used, where the switching function is performed by a temperature-sensitive element. Older units use electromagnetic devices with a moving core. If this element fails, the starting winding circuit does not close, and the rotor remains motionless, producing only a hum. Protective relay, often combined with the starting one, at this moment should break the circuit, preventing the engine from burning out.
⚠️ Attention: Prolonged operation of the compressor without a normally functioning starting mechanism leads to overheating of the windings and destruction of the insulation, which makes further repairs economically unfeasible.
Understanding the principle of operation helps to realize that you cannot simply short-circuit the wires - the engine will burn out in seconds. It is necessary to simulate the operation of the relay: apply current to the starting winding, wait for the shaft to spin up and immediately turn it off. This process requires precise timing or the use of special push-button mechanisms.
Fault diagnosis before intervention
Before trying to start the refrigerator bypassing the standard circuit, you need to make sure that the problem lies in the relay, and not in the compressor or wiring itself. Primary diagnosis begins with a visual inspection and listening to the sounds made by the unit when trying to turn on. If a characteristic click is heard, followed by a hum, and after a few seconds another click (the protection is triggered), this is a classic sign of a malfunction of the starting unit.
Next is checking the integrity of the motor windings using a multimeter. It is necessary to remove the compressor cover and disconnect the wires from the relay. By measuring the resistance between the contacts, you can identify turn-to-turn short circuit or a break. Normal resistance readings for different windings may differ, but they should not be zero or infinite (depending on the type of measurement).
- 🔍 Check the resistance between the common contact and the working terminal - it should be minimal.
- 🔍 Measure the starting resistance windings - it is usually higher than that of the working one.
- 🔍 Make sure there is no breakdown on the case (the resistance between the contacts and the copper tube should be infinite).
If the diagnostics show that the windings are intact, and the relay does not click or is stuck, you can consider the option of a temporary start. However, if the multimeter shows a short circuit or open circuit inside the engine, any attempts to start without replacing the compressor are useless and dangerous. The table below shows typical resistance values for serviceable engines from different manufacturers.
| Compressor model | Working winding resistance (Ohm) | Starting winding resistance (Ohm) | Relay type |
|---|---|---|---|
| Atlant CKN-10 | 28-32 | 40-45 | Posistor |
| Danfoss BD35F | 12-15 | 25-30 | Electronic |
| Embraco EMT6150 | 18-22 | 35-40 | Electromagnetic |
| Indesit CBI | 20-25 | 30-35 | Posistor |
Motor winding connection diagram
For a successful start, you need to clearly understand which wires go where. Most single-phase compressors have three terminals: Common, Run and Start. A connection diagram without a relay involves supplying voltage to the common and working contacts constantly, and to the starting contact only at the moment of start.
Usually the wires are color-coded, but you should not rely on it alone, since manufacturers can change the standards. It is most reliable to identify contacts by resistance or markings on the terminal block (C, R, S or L1, L2, L3). Common wire most often has the lowest resistance in relation to the other two contacts in total.
Color marking of wires (for reference)
Often the common wire is white or black, the working wire is green or red, the starting wire is blue or yellow. However, in Chinese compressors the colors can be any, so a test with a multimeter is required.
When organizing a temporary connection, it is important to use wires with a cross-section of at least 1.5 mm² so that they do not heat up under load. All connections must be securely insulated, preferably using terminal blocks or high-quality electrical tape. Improvised twisting "on the snot" at currents of 5-10 amperes can cause a fire.
Methods for temporarily starting a compressor
There are several ways to start the engine bypassing the standard relay. The simplest, but riskiest method is to use a normally open button. The button is connected to the break in the starting winding circuit. When applying power to the main windings, you briefly press the button, giving a start impulse, and immediately release it.
A more advanced option involves using a capacitor of suitable capacity, which creates the phase shift necessary for start. The capacitor is connected in parallel with the starting winding and also requires disconnection after a set of revolutions, or a special circuit with a current relay is used. This method is softer for the engine, but requires precise selection of capacitance.
- ⚡ Button method: requires precise operator response, risk of not having time to turn off the starting winding.
- ⚡ Capacitor method: more stable, but requires additional equipment.
- ⚡ Using a universal relay: installing a new cheap relay - the most correct way.
⚠️ Attention: The time to turn on the starting winding should not exceed 1-3 seconds. If the engine does not start, you can try again no earlier than after 5-10 minutes to avoid overheating.
If you use a button, keep your finger ready to instantly open the circuit. As soon as the motor shaft spins and the sound of operation changes to a smooth hum, the starting winding circuit must be immediately broken. If you wait too long, the starting winding will burn out, and the compressor will have to be thrown away.
☑️ Checklist before starting
Safety precautions and risks
Operating a refrigerator with a connection "directly" or through a makeshift scheme carries serious risks. The main one is the lack of thermal protection. The standard relay often functions as a thermal relay, turning off the motor when it overheats. In a homemade circuit, this function must be controlled visually or by ear, which is inconvenient and dangerous.
In addition, the tightness of the system is compromised if the tubes were unsoldered for diagnostics, or the risk of electric shock simply increases due to open connections. Refrigerant the system is under pressure, and any sparks near places of possible leaks (although freon is not always flammable, oil can ignite) are unacceptable.
It is also worth considering that starting without the correct phase shift (if you simply apply 220V to the working winding) may not provide the required torque. The engine will hum and vibrate, but will not start, consuming huge current. This will quickly lead to the operation of the circuit breakers in the panel or melting of the wiring.
When you need to call a technician
Independent manipulation is justified only if you have knowledge in electrical engineering and understand what you are doing. If, after checking the windings and trying to start the engine with a button, the engine still does not start, the problem may be deeper - a mechanical wedge of the piston group or loss of compression.
In such cases, further attempts to “wedge” the motor with a hammer or by applying increased voltage will only lead to final failure. A professional technician has the equipment to vacuum the system, refill with freon and replace the compressor using soldering technology.
⚠️ Attention: If you are not confident in your abilities, do not take risks. An incorrect connection can cause a short circuit in the home network, which will lead to a fire or failure of other equipment.
The cost of a new starting relay is relatively low, and its replacement is a standard repair procedure. An attempt to save on relays using complex bypass circuits often leads to the need to purchase a new compressor, which costs several times more.
FAQ: Frequently Asked Questions
Is it possible to leave the refrigerator running without a relay all the time?
No, this is strictly prohibited. Without a starting relay (or its high-quality analogue), the engine will not be able to start correctly and, more importantly, will not be protected from overheating. This will lead to the windings burning out within a short time.
What capacitor is needed to start the compressor?
Usually starting capacitors with a capacity of 20 to 50 μF with a voltage of at least 250V (preferably 450V) are used. The exact capacity depends on the power of a particular engine and is indicated in the technical documentation.
Why does the compressor hum, but does not start even with a button?
This may indicate a mechanical wedge of the piston group, a break in the starting winding, or insufficient voltage in the network. It is also possible that the time for pressing the button was chosen incorrectly.
Is it dangerous to touch the compressor housing during such diagnostics?
Yes, it is dangerous. If the insulation is broken or there is a breakdown on the housing (which often happens in old motors), a phase voltage of 220V may appear on the metal housing, which is deadly for humans.