A sudden breakdown of refrigeration equipment often takes you by surprise, especially when there are perishable products left inside. One of the most common causes of compressor failure is the failure of the starting device, known as starting relay. In older models of domestic and foreign refrigerators, such as Atlant, Biryusa or Minsktype P1 was often installed, which is responsible for starting the engine and protecting against overloads. If you hear a characteristic click, after which the engine hums but does not start, or the compressor is completely silent, the problem most likely lies in this component.
Independent replacement of the P1 relay is a task that can be completely accomplished without calling a technician, if you follow safety precautions and have a minimum set of tools. Correct connection will restore the operation of the unit and extend the life of the compressor. In this article we will analyze in detail the relay device, methods for diagnosing it and a step-by-step replacement algorithm.
However, before starting any manipulations, you need to make sure that the problem is really in the relay, and not in the motor or wiring itself. Incorrect diagnosis can lead to the purchase of unnecessary parts or, worse, damage to a working compressor due to careless handling. Therefore, the first step should always be a visual assessment of the condition of the device and checking the voltage in the network.
Design and principle of operation of relay P1
Relay P1 is an electromagnetic device that closes the circuit of the compressor starting winding at the time of startup. As soon as the motor rotor reaches the required speed, the current in the working winding drops, and the relay opens the contacts of the starting circuit. Starting relay also performs a protection function: if the current exceeds the permissible values (for example, when the engine is jammed), the device opens the circuit, preventing the windings from burning out.
Structurally, relay P1 consists of an inductor, a movable core and contacts. Inside the case there is contact group, which closes and opens under the influence of a magnetic field. It is important to understand that these devices are designed for specific current characteristics. Installing a relay with inappropriate parameters can lead to frequent false shutdowns or, conversely, an inability to start the compressor.
⚠️ Attention: There may be a capacitor inside the housing of relay P1. Even after being disconnected from the network, it is able to retain its charge. Be careful when opening the case and do not touch live parts with your fingers without first discharging the capacitor.
In modern modifications there are solid-state analogues, but the classic P1 remains mechanical. Mechanical wear of contacts is the main reason for their failure. Over time, carbon deposits form on the metal surface, increasing resistance, which leads to heating and sticking of contacts. That is why timely replacement or cleaning of contacts can save the situation.
What is the difference between P1 and RTP?
Relay P1 usually has a vertical arrangement of contacts and is attached directly to the compressor, while RTP (Thermal Start Relay) often has an external thermal element and is mounted on a bracket. However, in everyday life they are often confused, since functionally they perform similar tasks.
Fault diagnosis before replacement
Before buying a new part or starting disassembly, it is necessary to determine exactly what the relay is to blame. The first sign of a malfunction is a characteristic sound: a series of clicks at intervals of several seconds or minutes. This means that the thermal relay is activated, opening the circuit, cools down and tries to start the engine again, but the starting relay does not perform its function.
For more accurate diagnostics, you will need a multimeter. Remove the relay from the compressor (after unplugging the refrigerator from the outlet) and inspect it for external damage: melted plastic, blackened contacts, burning smell. If there are no visual defects, proceed to testing the contacts. Resistance between the contacts should be close to zero in the closed state and infinite in the open state.
- 🔌 Check the integrity of the wires going from the relay to the compressor - they should not be broken or oxidized.
- 🔨 Lightly tap the relay on a hard surface: if something rattles inside, it means the mechanism is destroyed and requires replacement.
- 📏 Measure the coil resistance: it must correspond to the passport data for the specific relay model.
- 👀 Inspect the contacts for carbon deposits: black the color indicates poor contact and sparking.
If after checking it turns out that the contacts are burnt, but the body is intact, you can try cleaning them with fine sandpaper or a needle file. However, this is a temporary measure: the structure of the metal is already damaged, and after some time the problem will return. The safest thing to do is to immediately install a new set.
Necessary tools and safety measures
Working with electrical appliances requires strict adherence to safety rules. The most important mistake is trying to repair a device connected to the network. Electric current 220 volt voltage is life-threatening, so the first step is to completely de-energize the refrigerator. Unplug the plug from the socket and make sure that access to it is limited so that no one accidentally turns on the device while you are working.
To replace relay P1 you will need a minimum set of tools. The main work can be done with screwdrivers and pliers. It is also useful to have a multimeter on hand to check the contacts and perhaps some electrical tape or heat shrink to insulate the connections if the wires are short.
☑️ Tools for replacing the relay
Pay attention to the condition of the wire insulation. If it is cracked or melted, simply replacing the relay will not be enough. It is necessary to strip the ends of the wires and, if necessary, extend them using high-quality insulation. The use of twists without solder or terminal blocks is not recommended, as sparking may occur at the contact point.
⚠️ Attention: Do not attempt to repair the relay if the housing is cracked or deformed. Violation of the tightness leads to moisture and dust getting inside, which is guaranteed to cause a short circuit the next time you turn it on.
Step-by-step instructions for connecting relay P1
The process of replacing relay P1 is quite simple if you act sequentially. First, remove the rear panel of the refrigerator to gain access to the compressor. It is usually secured with latches or screws. After removing the cover, you will see a black cylindrical tank - this is a motor-compressor, and there is a relay on the side or top of it.
Carefully remove the old relay. It can be held on by latches, screws, or simply sit tightly on the contacts of the compressor. Remember or take a photo of which wire is connected where. Relay P1 usually has three main contacts: one goes to the starting winding, the second to the working winding, the third is common or grounding. The connection diagram of relay P1 strictly depends on the marking of the contacts on the body itself and the wiring of the refrigerator wires.
Install the new relay in place of the old one. It should fit tightly on the contacts of the compressor. Connect the wires according to the diagram: usually the phase wire goes to the relay input, and the output is distributed to the windings. If you are in doubt about the color marking of the wires, focus on the contacts on the old relay.
| Contact on the relay | Purpose | Wire color (typical) | Where to connect |
|---|---|---|---|
| 1 (Input) | Power | Brown / Red | From Thermostat |
| 2 (Start) | Start winding | Black / Blue | Contact "P" of the compressor |
| 3 (Operation) | Working winding | White / Green | Contact "P" of the compressor |
| Grounding | Protection | Yellow-green | Compressor housing |
After connecting all the wires, securely attach the relay to the compressor. Make sure it is not loose and there is no tension on the wires. Tension can lead to contact separation when the motor vibrates. Close the protective panel and turn on the refrigerator.
Typical installation errors and their consequences
One of the most common errors is incorrect positioning of the relay. Relay P1 is often sensitive to the installation position (arrow "UP" or "DOWN" on the housing). If you install it upside down, gravity will not help open the contacts, and the starting winding will remain on constantly. This will lead to rapid overheating and burning of the compressor winding.
Another common problem is poor contact at the junction of the wires. If you simply twist the wires or tighten the screws loosely, heat will be generated at the contact point. Over time, this will lead to melting of the insulation and possible fire. Always use high-quality connectors or soldering.
- ❌ Ignoring the condition of the wires: installing a new relay on old, oxidized wires is useless.
- ❌ Wrong relay type: installing a relay with a different operating current (for example, RKT instead of P1 without recalculating the parameters).
- ❌ Lack of fixation: if the relay is not secured, vibration will destroy the contacts inside it in a matter of days.
It is also important not to confuse the starting and operating windings when connecting. Although the design of the connectors often prevents error, the risk is greater when using universal relays or adapters. Connecting power to the starting winding directly will damage the motor almost instantly.
Checking operation and starting the system
After assembly, the moment of truth comes - the first start. Plug in the refrigerator. You should hear a firm click from the relay, followed by the smooth hum of the compressor running. After 10-15 seconds, the hum may change slightly - this is normal, since the relay opens the starting circuit and the engine switches to operating mode.
Pay attention to the current consumption if you have access to measuring instruments. The current may be high at start-up, but it should quickly drop to the rated value. If the compressor hums but does not start, or starts and immediately stalls, immediately turn off the power. This is a signal that the problem may be deeper: the compressor is jammed or the condenser is faulty.
During the first hours of operation, monitor the temperature of the compressor housing. It should be warm, but not so hot that you can't touch it. Excessive heating may indicate an overload or problems with refrigerant circulation, which relay P1 will not correct.