The situation when refrigerator stops freezing, and instead of the usual hum of the motor you hear only quiet clicks or a hum lasting a few seconds is familiar to many. Most often, this is due to the failure of start protection relay a small but critical element of the engine starting system. This device is responsible for supplying voltage to the starting winding of the compressor at the moment of switching on and protects the motor from overloads.
Independent replacement or installation of this component is possible, but requires strict adherence to safety precautions and an understanding of the operating principle single-phase motor. Errors in connection can lead to burnout of the compressor windings, which will turn a simple repair into an expensive replacement of the entire unit. Therefore, before starting work, it is necessary to study the structure of the mechanism and prepare tools.
In this article we will look at how to determine the malfunction, remove the old element and correctly connect a new relay to the compressor terminals. We will look at the differences between induction and posistor models, and also pay attention to the marking of contacts, which often confuses inexperienced craftsmen.
Principle of operation and types of starting devices
Start relay performs the function of a switch that briefly supplies current to the starting winding electric motor, creating the necessary torque. As soon as the rotor reaches about 75% of the rated rotation speed, the device automatically opens the starting winding circuit, and the engine continues to operate on the working winding. If this moment does not come on time, the windings may overheat.
There are two main types of devices used in household appliances: induction (electromagnetic) and posistor (thermal). Induction relays work due to electromagnetic force: current in the operating winding creates a magnetic field that draws in the core and closes the contacts of the starting circuit. When the current decreases, the core falls under the influence of gravity, opening the circuit.
Posistor relays use the property of a semiconductor material (posistor) to sharply increase resistance when heated. At the moment of switching on, a cold posistor has low resistance and passes current. Heated by the passing current, it becomes a dielectric, interrupting the starting winding circuit. Protective relay Often combined with the starting winding in one housing, reacting to temperature or overload current.
What is the difference between RKT and RTP?
RKT are old-style induction relays, often with a copper coil. RTP - thermal, where a bimetallic plate is used. Modern refrigerators are often equipped with combined posistor devices.
Diagnostics of faults before replacement
Before disassembling the equipment and buying spare parts, you need to make sure that the problem lies in the starting mechanism. A characteristic sign of a malfunction is when the compressor tries to start, it hums for 3-5 seconds, then a click is heard and the motor stops. After some time, the cycle repeats. This indicates that the engine does not receive an impulse to start or cannot reach operating mode.
Visual inspection of the removed element can tell a lot about its condition. If you find melted plastic, blackened contacts, or hear the contents rattling when shaken (in the case of a posistor), then relay replacement it is inevitable. It is also worth checking the integrity of the wires going to the contact group.
For accurate diagnostics, you can use a multimeter. By ringing the contacts, you can identify an open circuit or, conversely, a short circuit.
- 🔍 Symptom 1: The refrigerator hums, but does not start, the thermal protection is activated after a few seconds.
- 🔥 Symptom 2: Traces of burning, melting or deformation are visible on the relay body plastic.
- 🔊 Symptom 3: When you shake the removed device, you can hear the ringing of broken internal elements (typical of ceramic posistors).
- ⚡ Symptom 4: The multimeter shows a lack of conductivity or a short circuit to contacts.
Preparation for work and safety measures
Repair of electrical appliances requires compliance with strict safety rules. The first and most important step is to completely disconnect the refrigerator from the power supply. It is not enough to simply turn off the device with the button - you need to unplug the plug from the socket. Any manipulation with live electrical components is deadly.
To perform the work you will need a minimum set of tools: a screwdriver (Phillips and flat-head), pliers, a multimeter for checking circuits and, possibly, a knife for stripping contacts. It is also recommended to have electrical tape or heat shrink on hand to insulate the connections.
⚠️ Attention: The compressor contains refrigerant under pressure. It is strictly forbidden to cut through or bend the copper tubes coming from the motor, as this will lead to a freon leak and will require calling a technician with a vacuum pump for refilling.
Make sure that the workplace is well lit and the space around the refrigerator is free. You can usually get to the compressor from the rear side of the unit, where the motor niche is located. In some models, you may need to remove the protective cover secured with screws or clips.
☑️ Preparation for repair
Removing the old starting relay
The process of removing a faulty element begins with visually fixing its position. It is highly recommended that you take several close-up photos of the assembly before disconnecting the wires. This will help to avoid errors during assembly, since the color marking of the wires may differ from one manufacturer to another.
Remove the relay from the compressor contacts. It can simply be put on three pins or fixed with a metal bracket-bar. If a bracket is used, it must be carefully pressed out or the fastening screw must be unscrewed. Proceed carefully so as not to damage the plastic elements or wires.
Disconnect the wires from the contact group. Depending on the design, wires can be inserted into connectors, soldered or fixed with screws. If the wires are soldered, they need to be carefully unsoldered, after remembering which wire went to which contact. Modern models most often use connectors that can be removed by hand or by gentle shaking.
After removing the device, inspect the contact pins on the compressor itself. They must not be oxidized or bent. If necessary, they can be carefully cleaned with fine sandpaper, but this must be done extremely delicately so as not to break the ceramic base.
Connection diagram and contact marking
The most critical stage is connecting the new device. Here it is important to understand the contact markings that are printed on the relay or compressor housing. The standard marking for most compressors is as follows: S (Start) - starting winding, R (Run) - working winding, C (Common) - common contact.
In some cases, especially on Soviet-made equipment or in For specific models, designations may vary. For example, numbers or color marks may be used instead of letters. Always check the technical documentation or the diagram printed on the electrical panel of the refrigerator.
The connection process consists of putting the wire connectors on the corresponding pins of the new relay, and then installing the entire assembly on the compressor terminals. It is important to ensure tight contact. If the connectors are loose, they should be carefully tightened with pliers, but not overdo it, so as not to split the insulator.
Below is a table of contact correspondence for common types of compressors, which will help you navigate the markings:
| Designation on the diagram | Function contact | Wire color (typical) | Location on the compressor |
|---|---|---|---|
| C (Common) | Common power input | Black or White | Top or left (depending on the model) |
| S (Start) | Start winding | Red or Blue | Middle or right |
| R (Run) | Working winding | Green or Yellow | Bottom or right |
| Ground | Ground case | Green with a stripe | Separate screw on the case |
⚠️ Attention: Incorrect connection of contacts S and R will lead to the compressor humming, but not starting, and after a short time the starting winding will burn out. Double-check the circuit three times before turning it on!
Starting and checking the operation of the refrigerator
After installing the new relay and connecting all the wires, assemble the protective cover of the engine compartment, but do not screw it tightly yet. Plug in the refrigerator. In the first seconds, you can hear a characteristic click and a smooth hum of the operating compressor. This is a good sign.
Pay attention to the current strength if you have a clamp meter. The starting current can be several times higher than the operating current, but it should quickly drop to rated values. If the humming continues for more than 5-10 seconds without switching to operating mode, immediately disconnect the device from the network.
Check the heating of the relay housing. During normal operation, posistor relays may become hot, but they should not smoke or smell like burning plastic. If everything went well, secure the casing and move the refrigerator to the place of permanent use.
Let the refrigerator operate for several hours without loading food to make sure the temperature is stable and there are no cyclic shutdowns. If the equipment runs smoothly and freezes, the repair can be considered successful.
What to do if the new relay clicks, but the compressor does not start?
Perhaps the problem is not in the relay, but in the compressor itself (interturn short circuit, jamming of the piston group) or in the capacitor (if it is in the circuit). Professional diagnostics are required.
Is it possible to install a relay from another refrigerator?
Installation of a relay from another model is possible only if the electrical characteristics (cut-off current, type: induction/posistor) and the geometry of the seat completely match. Using an unsuitable analogue can lead to damage to the compressor.
Why does a new relay burn out immediately after installation?
A common reason is poor contact in the connectors or a malfunction of the compressor itself (for example, increased starting current due to wear). Also, the relay can burn out if the contacts of the starting and working windings are reversed.
Is it necessary to change the relay if the refrigerator is working, but it is heating up?
A slight heating of the relay body during operation is normal, especially for posistor models. You should sound the alarm only if the housing becomes so hot that it is impossible to touch it, or a burning smell appears.
How to determine that the problem is in the relay, and not in the compressor?
If, when turned on, the compressor hums for 3-5 seconds and clicks, most likely it is the relay. If it hums constantly and gets very hot, but does not click, the compressor may have jammed or the winding has burned out. Testing the windings with a multimeter will give an accurate answer.