Starting compressor the refrigerator directly is a standard diagnostic procedure that allows you to determine whether the motor itself is working or the problem lies in the control system. Often the refrigerator stops freezing not because of a freon leak or a breakdown of the engine itself, but due to a failure of the start relay or thermostat. In such a situation, direct start allows you to isolate the unit and understand the further repair strategy.
However, it is worth remembering that direct connection to a 220 volt network is a stress test for the unit. In normal operation, the electrical circuit breaks and closes automatically, but when started manually, the responsibility for monitoring the operating time and temperature of the windings falls on the master. Incorrect actions can lead to the final combustion of an expensive unit.
Before starting work, you must clearly understand the risks. Electric current dangerous to life, and the refrigerant inside the system is under pressure. If you do not have minimal skills in working with electrical appliances, it is better to refrain from intervening on your own. This instruction is for informational purposes only and describes the principles of operation of the electromechanical part of refrigeration units.
Principle of operation and design of the starting mechanism
To understand how to start motor without standard automation, you need to understand its internal structure. Compressors for household refrigerators are usually asynchronous electric motors with a starting winding. To start them, the creation of a rotating magnetic field is required, which is provided by the starting device. In classic models, this role is played by starting relaywhich mechanically or electronically switches the windings.
At the moment of switching on, current passes through the starting winding, creating the necessary torque. As soon as the rotor picks up speed, the relay opens the starting winding circuit, and the engine continues to operate on the main winding. If the relay is faulty, this cycle is disrupted: either the starting pulse is not supplied, or the starting winding remains on, which leads to its overheating and activation of the thermal protective device.
⚠️ Attention: The thermal protection relay can only operate again after the compressor has completely cooled down (usually 15-20 minutes). Attempts to frequently turn on a “hot” motor will lead to irreversible damage.
There are two main types of starting devices: posistor and induction. The posistor ones work by changing the resistance of the heating element, while the induction ones use electromagnetic force to open the contacts. Understanding the type of your relay will help in choosing a method for emulating its operation when connected directly.
What is the difference between the compressor windings?
The starting winding has a thinner wire and higher resistance (if measured with a multimeter on some models, although more often the opposite is true - the working winding is thicker, but there are more turns, so the starting resistance is often higher). The service winding is designed for long-term operation and has a lower resistance. Mixing up the pins when connecting can lead to a humming noise and lack of shaft rotation.
Required tools and precautions
To carry out high-quality diagnostics, you will need a minimum set of tools. First of all, this multimeter (tester) is for checking the integrity of the windings and the absence of breakdown on the housing. Without this device, a “blind” connection is categorically not recommended, since the risk of a short circuit is too great.
You will also need tools to dismantle the casing and terminal box: screwdrivers (Phillips and flat-head), side cutters or wire cutters, insulating tape and possibly pliers. For the connection itself, pieces of copper wire with stripped ends or special clamps are often used.
- 🛠️ Multimeter —required for testing the circuit and measuring resistance.
- 🔌 Cord with plug —for supplying voltage (preferably with a built-in switch).
- 🧤 Dielectric gloves —additional protection against electric shock.
- 📋 Connection diagram —often printed on the relay cover or in the instructions.
Pay special attention to the condition of the wire insulation. If the wires show cracks or melting, they must be replaced before testing begins. Working with bare wires under a voltage of 220 volts is unacceptable.
Wire connection diagram and pinout
There are three contact terminals on the compressor body, which are usually covered with a plastic cover. These leads go to the motor windings. To connect correctly compressor, you need to identify each of them: Common, Start and Run. An incorrect connection will cause the motor to hum but not start, or the starting winding will burn out.
Determining the terminals is done by measuring the resistance between pairs of contacts. Between the working and starting terminals the resistance will be maximum (the sum of the resistances of both windings). Between general and working - minimal (working winding). Between the general and starting - the average value.
Below is a table that helps you navigate the resistance values for a standard single-phase motor:
| Pair of contacts | Winding type | Expected resistance (Ohm) | Purpose |
|---|---|---|---|
| General - Working | Working | 10 - 25 Ohm | Main power |
| General - Starting | Starting | 20 - 40 Ohm | Starting impulse |
| Working - Starting | Total | 30 - 65 Ohm | Full circuit |
| Any - Housing | Breakdown | Infinity | Isolation |
It is important to note that the location contacts on different models (for example, Atlant, Indesit or Beko) may differ. Sometimes the conclusions are marked with letters: C (Common) - general, R (Run) - working, S (Start) - starting. In European models, designations may be used 1, 2, 3.
Step-by-step instructions for directly starting the engine
The starting process requires care and adherence to the sequence of actions. First you need to remove the start relay from the compressor contacts. Usually it is simply put on the terminals and secured with a bracket or clamp. After dismantling the relay, three pins of the outputs become visible.
Next, you should prepare a temporary connection diagram. To do this, one wire from the network is connected to the common terminal (phase or zero, in this case there is no difference for alternating current, but it is better to observe the color coding). The second wire from the network is connected to the working terminal. The starting terminal remains free for now.
☑️ Action algorithm
A short-term short circuit is used to create a starting pulse. One end of the wire from the starting terminal briefly touches the second network wire (parallel to the working one). At this moment, a click is heard and the engine starts. After starting, the starting winding wire must be removed immediately.
⚠️ Attention: You cannot hold contact on the starting winding for more than 2-3 seconds! This will lead to instant overheating and burning of the starting winding, since it is not designed for long-term operation.
If the motor starts and runs smoothly, without strong vibration and hum, then the unit itself is working, and the problem was in the relay or thermostat. If you hear a hum, but there is no rotation, the mechanical part may be jammed or the starting winding is faulty.
Diagnostics of faults by sound and behavior
Successful launch is only half the battle. It is necessary to analyze how one behaves unit at work. A working compressor operates with moderate noise, which increases smoothly. After a few minutes of operation, the outlet tubes should begin to heat up, and cold will appear in the evaporator (inside the refrigerator).
If you hear a loud humming sound when you turn it on, but the shaft does not rotate, this indicates a mechanical wedge or a severe voltage imbalance. In some cases, it is possible to “unwedge” the motor using the shock method (sharp voltage pulse), but this is a temporary measure. A long hum without rotation indicates that current flows through the windings, creating a magnetic field, but the rotor cannot overcome the resistance.
It is also worth paying attention to the current consumption. If it is possible to connect an ammeter to the open circuit, check the current strength. It should not exceed the nominal values indicated on the compressor nameplate (usually 0.5 - 1.5 Amperes for household models). Excess current indicates an interturn short circuit.
Replacement of the starting relay and final assembly
If the direct start was successful, the next task is to install a new start relay. The old relay is most likely faulty if it did not provide automatic start. When purchasing a new part, pay attention to the markings and engine power indicated on the housing (for example 1/5 HP, 1/4 HP). Universal relays are often suitable for many models, but it is better to look for the original or a complete analogue.
Installation is done in the reverse order: the relay is put on the compressor terminals until there is a characteristic click or a tight fit. Then the ground terminal (if any) is connected and the bracket is fixed. It is important to check that the wires do not touch the hot parts of the motor.
After assembly, turn on the refrigerator and check the first cycle of operation. The thermostat should automatically turn off the compressor when the set temperature is reached. If the refrigerator operates non-stop and does not turn off, the thermostat itself or the defrost sensor may be faulty.
⚠️ Attention: Technical characteristics of compressors and requirements for relays may vary depending on the manufacturer and year of manufacture. Always check the markings of the new part with the original before installation.
Frequently asked questions (FAQ)
Is it possible to leave the refrigerator running without a start relay?
No, it is not possible. Without a relay, the starting winding will not turn off after the start, which will lead to its burning out in a few seconds, or the motor will not start at all. The relay is a necessary element of the circuit.
Why does the compressor hum but does not start?
The most likely reasons: jamming of the mechanical part of the compressor, breakage of the starting winding or a malfunction of the starting relay (does not supply a starting pulse). Also, the reason may be low voltage in the network.
Is it dangerous to connect the compressor directly on a permanent basis?
Yes, it is dangerous. Direct connection bypassing the relay and thermostat deprives the system of protection against overheating and overloads. This is only permissible for short-term diagnostics (for a few minutes), but not for continuous operation.
How to understand that the compressor has burned out?
If, when tested with a multimeter, the resistance between the terminals shows infinity (open circuit) or zero (short circuit), or if there is a breakdown to the housing, the compressor is considered faulty and requires replacement.