A sudden stop of the refrigerator often becomes an unpleasant surprise, especially when there are perishable foods left in the chamber. If the unit has stopped cooling, but continues to hum or, conversely, is silent, the problem may be hidden in the compressor starting system. One of the key elements of this system is the start-protection relay, which is responsible for supplying voltage to the motor windings at the time of start.
Understanding how to check the refrigerator start relay will allow you to independently diagnose the breakdown and, perhaps, avoid an expensive call to the technician. In this article we will analyze in detail the device of the component, methods for checking it with a multimeter and visual diagnostics. You will learn to recognize signs of a malfunction and safely replace the part if necessary.
Design and principle of operation of a start-up protection relay
The start-up protection relay is a compact electromechanical device that is installed directly on the compressor housing. Its main task is to briefly apply voltage to the starting winding of the motor to create the necessary torque, and turn it off when the rotor reaches the desired speed. At the same time, the device performs a protective function, opening the circuit in case of overload or overheating.
In modern refrigerators, two types of relays are most often found: posistor (PTC) and induction. Posistor models operate on the basis of a ceramic element, which sharply increases its resistance when heated by current, actually opening the circuit of the starting winding. Induction ones use an electromagnetic coil and a movable core, which mechanically opens the contacts when a certain current is reached.
Despite the simplicity of the design, this component is subject to constant loads. Switching on and off cycles, voltage surges in the network and natural wear and tear of materials lead to the fact that the relay fails. Understanding operation principle the specific model of your equipment (for example, Indesit or Atlant) will help you quickly navigate the nature of the fault.
- 🔌 PTC relays do not have moving parts, which means makes them more durable, but sensitive to shock.
- ⚙️ Induction models use mechanical opening of the contacts, which over time can lead to their sticking.
- 🌡️ The protective function is triggered when the rated current is exceeded, preventing combustion of the compressor windings.
Primary visual diagnostics and signs of malfunction
Before picking up measuring instruments, it is necessary to conduct an external inspection. Often characteristic signs of breakdown are visible to the naked eye or audible. If the refrigerator hums but does not start, or starts for a couple of seconds and immediately stalls with a click, these are classic symptoms of problems with the starting equipment.
Remove the rear protective panel of the refrigerator and locate the compressor. The relay is usually mounted on the side of the motor and covered with a plastic casing. Carefully remove the casing and disconnect the wire block. Carefully inspect the relay body: there should be no cracks, traces of burning, melting or soot on it. Any burning smell is a sure sign that the part requires replacement.
⚠️ Attention: If you find traces of oxidation or blackening on the relay contacts, this indicates poor contact, which could cause overheating and failure of the entire starting circuit.
It is also worth shaking the relay near your ear. If a clear knocking or rattling noise is heard inside, this may mean that the posistor has crumbled or the mechanical parts have moved. However, the absence of sound does not guarantee serviceability, so we move on to more accurate methods.
- 👀 Look for visual defects: cracks, swelling, signs of overheating on the plastic.
- 👃 The smell of burning plastic or insulation is a clear signal of a burnt element.
- 👂 A characteristic click when trying to start, after which the compressor goes silent, indicates that the protection has activated.
Preparing for testing with a multimeter
For accurate diagnostics, you will need a digital multimeter. This is a universal device that allows you to measure resistance, voltage and circuit integrity. Before starting work, make sure that the refrigerator is completely disconnected from the power supply. Safety is the number one priority when working with electrical appliances.
Remove the relay from the compressor. To do this, it is usually enough to simply pull it down or slightly rock it from side to side, after unscrewing the fixing screws, if any. Pay attention to the orientation of the part: the top should be on top, the bottom should be on the bottom. This marking is important for correct installation back.
Set the multimeter to the resistance measurement mode (Ohm), selecting a limit of 200 Ohm. If your device has a dialing mode with a sound signal, this will greatly simplify the task. Clean the relay contacts from possible deposits to ensure a reliable connection of the probes.
☑️ Preparation for diagnostics
Methodology for checking a posistor relay
Checking a posistor relay (PTC) consists of measuring the resistance between certain contacts. Most models have three main contacts: two for connecting to the compressor (often labeled 1 and 2 or M and S) and two for connecting to the mains. The resistance between the contacts going to the starting winding should be in the range from 20 to 60 Ohms.
If the multimeter shows one (infinity) or zero, then the posistor is faulty. It is also important to check the integrity of the protection circuit. The resistance between the contacts going to the main winding should be close to zero (short circuit mode), since it is just a bimetallic plate in a cold state.
There is a nuance: after testing, the posistor heats up and its resistance increases sharply. To recheck, you need to let it cool for 10-15 minutes. If you take measurements and get strange results, wait and try again when the part has cooled to room temperature.
Why does the relay heat up during testing?
When voltage is applied, current begins to flow through the posistor, causing it to heat up. This is a normal operating process, due to which the starting winding circuit is opened. However, when not in operation, it must be cold.
For clarity, we present typical resistance values for different types of relays:
| Relay type | Starting circuit resistance | Protective circuit resistance | Status |
|---|---|---|---|
| Posistor (serviceable) | 20–60 Ohm | 0 Ohm (ringing) | Working |
| Posistor (burnt) | Infinity (1) | 0 Ohm | Faulty |
| Induction | Depends on the coil | 0 Ohm | Requires checking contacts |
| With insulation breakdown | 0 Ohm (short circuit) | Any | Dangerous for networks |
Diagnostics of induction relays
Induction relays, often found in older models of refrigerators Zil or Biryusa, are more complex. Inside them there is a coil and a movable core. Testing such a relay with a multimeter shows the coil resistance, which is usually several ohms. However, the main thing here is the mechanical part.
It is necessary to check whether the core moves freely. If it is stuck in the upper position, the contacts of the starting winding will not open, which will lead to an overload. If it is in the lower position, the engine will not start. Visually inspect the contacts: they should be clean and free of carbon deposits. If necessary, they can be carefully cleaned with fine sandpaper, but it is better to replace the entire relay.
Checking the continuity of the circuit in the induction relay is also important. When cold, the main circuit contacts must be closed. When current is applied (which is difficult to check at home without a stand), the core should retract and open the starting circuit. If the coil rings, but there is no mechanics, the relay needs to be replaced.
⚠️ Attention: Do not try to forcibly move the induction relay core with tools. The mechanism is very delicate and can easily be damaged by violating the calibration.
Replacement and installation of a new relay
If diagnostics show a malfunction, the only correct solution is replacement. Repairing the internal components of the relay at home is neither possible nor practical, as it requires factory calibration. Buy an analogue that fully matches the markings of your old device.
Installation is carried out in the reverse order of removal. Push the relay onto the compressor contacts until it stops. Make sure the "UP" marking or arrow is pointing straight up. This is critical for proper operation of the gravity contact opening mechanism. Attach the retaining strip or screws.
Connect the wires to the terminal block, following the color markings or photographs taken earlier. After assembly, plug in the refrigerator. The compressor should start with a characteristic hum, after a few seconds the click should repeat (disabling the starting winding), and the unit will go into operating mode.
After replacement, it is recommended to monitor the operation of the refrigerator for a period of time first hours. It should reach the temperature and turn off when the set parameters are reached. If the problem persists, the compressor itself or the thermostat may be faulty.
Frequently asked questions (FAQ)
Is it possible to start a refrigerator without a relay?
Technically, you can start a compressor without a relay by applying voltage directly to the starting and operating windings, but this is strictly not recommended for continuous use. This will deprive the motor of overload protection and may cause it to burn out quickly. This method is used only for short-term diagnostics.
Why does a new relay burn out immediately after installation?
If a new relay burns out quickly, the reason may not be in it, but in the compressor itself. An interturn short circuit in the motor windings creates an increased current, which melts the relay contacts. Also, the cause may be power surges in the network or incorrect installation (wrong orientation).
Where can I find the markings to purchase a replacement?
The markings are usually applied to the side or top of the plastic relay housing. If the inscription is erased, the number can be found in the technical documentation of the refrigerator or searched by the model of the compressor itself, which is indicated on the sticker on its body.
How much does it cost to replace the relay by a specialist?
The cost consists of the price of the part itself and the work of the specialist. Depending on the region and model of the refrigerator, the price may vary. Replacing it yourself allows you to save on the cost of work, since the component itself is relatively inexpensive.