Sudden stoppage of operation of a refrigeration unit often becomes an unpleasant surprise, especially when inside there are perishable products. In most cases, the cause of the breakdown is the failure of starting relay a small but critical element of the compressor electrical circuit. This device is responsible for starting the engine and, in conjunction with a capacitor, provides the necessary phase shift for rotor rotation.
Understanding how to connect a refrigerator relay with a capacitor will allow you to fix the fault yourself, saving a significant amount on calling a technician. The replacement process does not require highly complex equipment, but it does involve working with live electric current, and therefore requires strict adherence to safety precautions and attention to detail.
In this article we will analyze the trigger mechanism, the diagnostic algorithm and the step-by-step process of installing a new component. You will learn how to correctly navigate the markings, choose the appropriate analogue and avoid common mistakes that can lead to repeated breakdowns or failure of the compressor itself.
Design and principle of operation of the starting unit
The starting relay is an electromagnetic or thermal switch that supplies current to the starting winding of the engine only at the moment of starting. As soon as the compressor rotor reaches the required speed, the relay opens the circuit and the engine continues to operate on the main winding. It often works in tandem with it capacitor, which creates an artificial third phase necessary to start an asynchronous motor.
There are two main types of such devices: posistor and induction. PTC relays operate by heating a ceramic element, which, when the temperature rises, sharply increases the resistance and breaks the circuit. Induction (electromagnetic) ones use the current flowing through the main winding to open the contacts when a certain current strength is reached.
A capacitor connected in parallel with the starting winding accumulates a charge and releases it at the moment of start, creating a powerful impulse. Faulty capacitor often leads to the hum of the compressor without subsequent starting, since the engine does not have enough torque to take off. It is important to understand that these elements work in conjunction, and replacing one without checking the other may be ineffective.
⚠️ Attention: Before starting any work, be sure to disconnect the refrigerator from the power supply. Even after switching off, a residual charge may remain in the capacitor, which can cause an electric shock. Close the capacitor contacts with a screwdriver with an insulated handle before touching.
Modern compressors often use combined devices, where the relay and capacitor are combined in one housing or located in close proximity to the terminal box. The design may vary depending on the manufacturer, be it Atlant, Indesit or Beko, but the principle of operation remains similar.
Why does the relay burn out?
A frequent cause of failure of the starting relay is not only natural wear, but also unstable voltage in the network, as well as jamming compressor piston group. If the compressor cranks tightly, the starting current increases many times over, which leads to overheating and destruction of the relay contacts or burnout of the posistor.
Diagnostics of the fault before replacement
Before buying new parts, you need to make sure that the problem lies precisely in the starting mechanism. Characteristic symptoms of a malfunction are characteristic clicks that follow at intervals of several seconds, after which the compressor hums but does not start. Also, the refrigerator may not respond at all to being turned on, although the light in the chamber is on.
For an initial check, remove the rear protective panel of the refrigerator and get to the compressor. Visually inspect the relay: if traces of melting, soot, or a burning smell are visible on the plastic housing, the part definitely requires replacement. However, external signs do not always appear, so a deeper check is necessary.
Remove the relay from the compressor contacts and shake it next to your ear. If a rattling sound is heard inside, this may mean that the posistor has crumbled or the contact has come off. For accurate diagnostics, use a multimeter in resistance measurement mode.
- 🔍 Continuity check: Ring the relay contacts - the resistance should be either close to zero (closed) or infinity (open) depending on the type and condition.
- ⚡ Thesistor test: For posistor relays, the cold element should have a low resistance, which increases sharply when heated.
- 🔋 Diagnostics of the capacitor: The capacitor should not short-circuit; the tester's arrow or readings should gradually increase, indicating charging.
If the multimeter shows a short circuit or open where there should not be one, the element is faulty. It is also important to check the compressor itself by ringing its windings through the contact group to exclude inter-turn short circuit of the motor.
Preparation for replacement and selection of components
The success of the repair largely depends on the correct selection of spare parts. Relays and capacitors are not universal devices; they are designed for a specific compressor power and type of refrigerant. Using an unsuitable analogue can lead to instant combustion of the new part or damage to the motor windings.
On the body of the old relay there is always a marking containing the catalog number, supply voltage (usually 220-240V) and permissible current. For example, the marking PTMRS 12A indicates a posistor relay with an operating current of 12 Amps. This data is critically important when searching for a replacement in stores or on radio markets.
Capacitors are selected by capacitance (uF) and operating voltage (V). The container should be the same as the original or differ by no more than 5-10%. The voltage must be equal to or higher than the rated voltage; using a capacitor with a lower voltage will lead to its explosion.
For work you will need the following tools:
- 🛠️ A set of screwdrivers (phillips and flat) for removing panels and clamps.
- 🔧 Pliers or pliers for removal terminals.
- 🔪 A utility knife or scissors for stripping wires (if required).
- 🧤 Dielectric gloves for additional safety.
If an exact analogue of the relay could not be found, you can use a universal starting relay. Such devices are equipped with a set of adapters and are suitable for most types of compressors. However, their installation requires careful study of the instructions included in the kit.
Step-by-step instructions for connecting a relay with a capacitor
The replacement process begins with dismantling the compressor protective casing. It is usually secured with latches or screws. Removing the cover, you will see a compressor with three contacts on which the old relay is attached. Carefully remove the lock (if any) and pull the relay down, disconnecting it from the contact group.
Carefully inspect the connection diagram. Wires are usually color coded, but you can't rely on color alone as manufacturers may use different standards. It is more important to focus on the location of the contacts: Start, working (Run) i Common.
If you install a universal relay or change the type of device, reconnection may be required wires In this case, it is better to cut the old wires, strip the ends and connect them to the new terminals using heat shrink or insulating tape. Twists in refrigerators are unacceptable due to vibration.
☑️ Procedure for replacement
The capacitor is usually mounted on a metal bracket next to the relay or directly on its body. When connecting a new capacitor, observe the polarity if indicated (although for starting capacitors in AC circuits this is often not critical, it is better to follow the markings). Connect one terminal of the capacitor to the start contact of the relay, and the second to the corresponding terminal of the compressor or relay, according to the diagram.
After physically connecting all the elements, put the assembled structure on the contacts of the compressor. It should fit tightly, without play. Make sure the relay is installed in the correct position: many models have a mark UP or an arrow pointing up. Violation of the orientation can lead to incorrect operation of the relay mechanics.
| Relay type | Contact marking | Connection feature | Application |
|---|---|---|---|
| Posistor (PTC) | 1, 2, 3 or M, S, R | Does not require strict orientation, but preferably vertically | Modern compressors |
| Induction | With coil and core | Only vertically, the core must move freely | Old models of refrigerators |
| Universal | Colored terminals | Requires selection of an adapter for the pins compressor | Replacement of burnt originals |
| With a capacitor | Additional outputs | You need to correctly connect the capacitance to the start circuit | Powerful compressors |
The final stage is assembly. Install the metal casing and secure it with screws or latches. Make sure the wires are not pinched or touching hot parts of the compressor. Only after complete assembly can you turn on the refrigerator.
Checking functionality and typical errors
After turning on the retail refrigerator, listen to the sounds. After a few seconds, the relay should click and the compressor should start with a characteristic hum. If the start-up was successful, after 10-15 minutes the tubes of the refrigeration unit will begin to heat up (at the outlet of the compressor), and cold will appear in the chambers.
One of the typical mistakes is the incorrect installation of the relay “upside down”. In such cases, the mechanical armature may stick and the relay will not open the starting winding. This will lead to overheating and burning of the compressor starting winding or the relay itself within a few minutes.
Another common mistake is ignoring the condition of the capacitor. Replacing a relay without replacing a swollen or lost capacitor often results in the new relay burning out at the first start due to overcurrent. Always change this combination in a comprehensive manner.
⚠️ Attention: If, after replacing the relay, the compressor hums for 3-5 seconds, clicks and turns off, and then the cycle repeats, immediately turn off the device. This may indicate a compressor wedge or an incorrectly selected relay. Long-term operation in this mode will kill the engine.
Also monitor the temperature of the relay housing during operation. It may get hot, but should not be hot. If the plastic begins to melt, it means that the contacts do not provide a reliable connection or the current exceeds the permissible limit.
Frequently asked questions (FAQ)
Is it possible to start the refrigerator without capacitor?
In most cases, starting a modern refrigerator without a starting capacitor will not work, especially if the compressor is powerful. The engine will not have enough torque to start, and it will only hum. Some low-power models may have a built-in starting circuit, but you should not rely on this - the absence of a capacitor will lead to overheating of the windings.
How to determine whether the compressor or relay has burned out?
If you hear a click, a hum, and a second click after a few seconds when you turn it on, most likely the problem is in the relay or the starting circuit. If the compressor is silent, but the relay clicks, or if the resistance of the compressor windings shows an open/short circuit when tested with a multimeter, the compressor itself is likely to fail.
Why does a new relay burn out immediately after installation?
There may be several reasons: the relay power (operation current) is incorrectly selected, the capacitor is faulty, creating an overload, or, worst of all, the compressor itself is seized. It is also possible that there is a short circuit in the refrigerator wiring or a power surge in the network.
Is it possible to use a relay from another refrigerator model?
You can use a relay from another model only if the electrical characteristics are the same: voltage, operating current and type (posistor/induction). The physical fit on the contacts must also match, otherwise you will have to resolder the wires, which is not always safe.