The situation when the refrigerator suddenly stops cooling food, often takes you by surprise, and the first sign of a malfunction is silence or a characteristic hum, which ends abruptly after a few seconds. In most cases, the reason for this behavior is the failure of the starting relay, which is responsible for supplying current to the compressor motor windings. Experienced technicians know that for short-term diagnostics or emergency start-up of the unit, you can use the direct connection method, bypassing the standard automation.
However, it is important to immediately understand that connecting the refrigerator directly is not a normal operating mode, but an emergency measure or diagnostic procedure. In the standard circuit, the relay protects the motor from overloads and ensures the correct start of the rotor, so removing this element requires the performer to be extremely careful and understand the physical processes occurring inside the electrical circuit.
This article is an expert guide based on many years of experience in servicing climate control equipment, and contains a detailed description of the actions necessary for safe work. We will analyze the device of the starting protection mechanism, consider the relay bypass circuit and provide a step-by-step algorithm of actions that will help you solve the problem of starting the compressor as soon as possible.
The principle of operation of the starting relay and fault diagnosis
The starting relay is a small plastic or metal block that is attached directly to the side of the compressor housing and connects to his contact group. Inside this device there are two main systems: a starting system, which briefly supplies voltage to the starting winding of the motor, and a thermal protection, which opens the circuit when it gets too hot. Modern models often use posistor relays, where the role of a switch is played by an element that sharply changes its resistance when heated by current.
Diagnostics begins with a visual inspection and listening to the operation of the unit. If you hear the compressor trying to start, making a humming sound, but after 3-5 seconds it clicks and goes silent, this is a sure sign that the starter is not engaging. Also, a malfunction may be indicated by the absence of a characteristic click of the relay when the refrigerator is turned on, which indicates a mechanical jamming of the contacts or an open circuit inside the housing.
For a more accurate diagnosis, you need to remove the relay from the compressor and shake it near your ear. If a ringing or knocking sound is heard inside, this means that the core or posistor has cracked and the device must be replaced. In some cases, the contacts may simply burn out, which can be seen when opening the case, however, to check the continuity of the circuit, it is better to use a multimeter in continuity mode.
Necessary tools and safety measures
Before you begin to interfere with the electrical circuit of the refrigerator, you need to ensure your safety and prepare the appropriate tools. Working with 220 volt electric current requires strict adherence to safety rules, since careless handling can lead to electric shock or short circuit.
You will need a minimum set of tools that a home craftsman usually has, but you may also need specific elements to create a temporary jumper.
To perform the work, prepare the following tools and materials:
- 🔧 Screwdrivers (Phillips and flat) for removing the back cover and dismantling the relay.
- 🔌 Multimeter or indicator screwdriver for checking the presence of voltage and continuity of circuits.
- 🧤 Dielectric gloves to protect hands when working with live wires in parts.
- 🔌 Insulating tape or casings for insulating connections.
- 🔧 Pliers for bending contacts or removing broken wires.
A critical step is disconnecting the refrigerator from the power supply. It is not enough to simply turn off the device with a button; if there is one, you must unplug the plug from the socket. Only after this can you remove the rear metal panel that blocks access to the compressor.
☑️ Safety check before starting work
Direct connection diagram of the compressor: step-by-step instructions
The direct connection process involves applying voltage directly to the working winding engine, bypassing the start relay. To do this, you need to gain access to the compressor contact group, which is usually hidden under a plastic cap or cover of the relay itself. Having removed the relay, you will see three or four contacts coming out of the motor housing.
The contacts on the compressor have standard markings, which may differ from one manufacturer to another, but most often they are designated in Latin letters. The main contacts are the working winding (R or M), the starting winding (S) and the common wire (C). To start the engine directly, we need to apply a phase to the common wire and the working winding, and close the starting winding briefly to create an initial torque.
Follow the following steps to start:
- Carefully remove the starting relay from the compressor contacts, disconnecting the power wires going to it.
- Determine the purpose of the contacts by checking the markings on the case or using a multimeter to search for paired windings.
- Prepare a temporary wire with a plug for connecting to a 220V network.
- Connect one end of the wire from the network to the contact
C(Common/General). - Connect the second end of the wire to the contact
R(Run/Working winding). - To start the engine, you need to briefly apply voltage to the starting winding
S(Start), using an insulated conductor or button.
⚠️ Attention: When connected directly, the thermal protection of the motor does not operate normally. If the compressor does not start within 3-5 seconds or begins to get very hot, immediately turn off the power to avoid burning out the windings.
Table of contact markings from different manufacturers
Different manufacturers of refrigeration equipment use their own contact marking system on compressors, which can confuse an inexperienced technician. Understanding these symbols is critical to correctly connecting wires and preventing short circuits. Below is a summary table of the main designations found in the most popular models of refrigerators.
When working with imported equipment, such as Liebherr, Bosch or Whirlpool, the marking can be applied directly to the contact strip or indicated in the technical documentation, which is sometimes located on the inner wall of the refrigerator compartment. Always double-check the correspondence of the contacts with a multimeter before applying voltage.
| Manufacturer | General (C) | Working (R) | Starting (S) |
|---|---|---|---|
| Atlant | C or 0 | R or P | S or L |
| Indesit | COM | RUN | START |
| LG / Samsung | C | M (Main) | S |
| Beko | C | R | S |
| Electrolux | 1 | 2 | 3 |
In some cases, especially on old Soviet compressors, the markings may be missing or erased by time. In such a situation, the common wire can be determined by the method of exclusion, measuring the resistance between pairs of contacts. The resistance between the working and starting contacts will be equal to the sum of the resistances of each of them relative to the common wire.
How to determine the windings with a multimeter without markings?
Set the multimeter to resistance measurement mode (2 kOhm). Measure the resistance between each pair of three contacts. The pair with the highest resistance is the work and start windings together. The third, remaining contact is the common wire (C). The resistance between common and working will be less than between common and starting.
Experimental launch and performance testing
Once the circuit is assembled and the wires are connected according to the markings, you can begin a test run. This stage is the most critical, since it is in these seconds that it becomes clear whether the compressor itself is alive or the problem lies deeper. Plug the plug into the outlet and carefully monitor the behavior of the engine.
If the compressor is working properly, you will hear a smooth hum of the running motor, and air will begin to flow from the tubes coming out of the housing. For a more accurate check, you can put your finger to the outlet of the discharge tube - you should feel a steady stream of air under pressure. If the motor hums but does not rotate, the piston group may be jammed or there is not enough starting torque.
In some cases, to start a “tired” motor, it is necessary to artificially create a starting impulse. This is done by short-circuiting the contact of the starting winding with the phase wire. The closing time should not exceed 1-2 seconds, otherwise there is a risk of burning the starting winding, which is not intended for long-term operation under voltage.
Check tightness and pressure is the next important step. If the compressor starts but there is little or no outlet pressure, this may indicate an internal freon leak or broken valves. In this case, a direct start will confirm that the electrical part is in good condition, but the unit itself requires complex repairs with replacement of the motor-compressor.
Possible risks and limitations of the method
Using the direct connection method carries certain risks that anyone who takes responsibility for repairing equipment should be aware of. The main disadvantage is the lack of thermal protection, which in a standard relay turns off the power if it overheats. With a direct connection, the compressor will operate until the internal fuse burns out or trips, if provided by the design.
In addition, incorrect identification of contacts can lead to a short circuit or voltage supply to the wrong winding, which is guaranteed to damage the engine. It is also worth considering that operation without a capacitor (if provided by the circuit) or with incorrect phasing can cause severe heating and vibration.
The main risks of direct connection:
- 🔥 High risk of overheating of the windings due to the lack of thermal protection.
- ⚡ Possibility of electrical shock electric shock if careless handling of exposed wires.
- 💥 Risk of fire in the wiring due to a short circuit at the connection point.
- 📉 Reduced compressor life due to frequent starts without a soft starter.
⚠️ Attention: Do not leave it turned on directly the compressor is left unattended, even for a short time. Constant monitoring of the temperature of the motor housing is mandatory: if it becomes too hot to touch with your hand, immediately turn off the power.
This method is only suitable for diagnosing or temporarily solving the problem before purchasing new parts. For continuous operation of the refrigerator, it is necessary to install a new start relay that matches the model of your compressor. Operation of the unit with a bypass connection scheme is prohibited by fire safety regulations.
Frequently asked questions (FAQ)
Is it possible to leave the refrigerator running without a relay all the time?
No, this is strictly prohibited. The starting relay provides not only engine start, but also protection against overheating. Operation without a relay will lead to rapid burnout of the compressor windings or fire of the wiring. Use this method only for a short-term check.
Why does the compressor hum, but does not start even with a direct connection?
There may be several reasons: jamming of the piston group (the compressor is “bitten”), a break in the internal winding of the motor or insufficient voltage in the network. It is also possible that the contacts of the starting and operating windings are incorrectly identified.
Where to find the contact markings if they have been erased on the housing?
If there is no marking on the contact strip, try to find a technical sticker on the compressor body itself (often round metal or paper). If there is no information there either, you will have to determine the windings by measuring resistance with a multimeter: total resistance = operating + starting.
Is it safe to use a homemade button to start?
Using a homemade button is only permissible for short-term diagnostics (for 1-2 seconds). This is unsafe for continuous operation due to the risk of contact sticking and lack of insulation. It is better to purchase a standard relay, which is inexpensive and guarantees safety.