Owners of household appliances often face a situation when the refrigerator Bosch stops cooling, although the motor seems to be trying to start. A distinctive clicking sound followed by silence or a humming noise usually indicates a problem with the compressor trigger mechanism. It is starting relay responsible for supplying a starting pulse and protecting the engine from overloads, so its localization becomes the first step in diagnosis.
In modern models of the German brand, this element is hidden from the user’s eyes, which creates the illusion of difficulty in repair. However, knowing the design features of the units Bosch, you can quickly determine the location of the unit without calling a technician. In most cases, the problem lies in the rear of the housing, where the compressor compartment is located.
Access to the insides of the refrigeration unit requires compliance with safety precautions. Before starting any manipulations, you must completely turn off the power to the device by unplugging the cord from the outlet. Ignoring this rule can lead to electric shock, since the relay is located in close proximity to live parts.
⚠️ Attention: Carry out work on finding and replacing the relay only after completely disconnecting the refrigerator from the power supply. Residual voltage in the capacitors may persist for several minutes after switching off.
The design of most refrigerators Bosch involves placing the compressor in the lower rear part of the case. The relay is mounted directly on the side or top of the motor-compressor casing. For a visual inspection, you do not need to disassemble the entire refrigerator; it is enough to gain access to the technical niche.
Design features of the unit location
The search for relays in units Bosch begins by examining the back wall. Unlike some budget models, where access may be limited by a removable panel, here you often just need to move the equipment away from the wall. Compressor It is a black metal tank to which copper tubes and an electrical cable fit.
A plastic box is attached directly to the compressor terminals (usually there are three of them) black or white. This is the desired device, which in technical documentation can be designated as start-protective relay. It combines the functions of starting the engine and thermal protection of the windings.
In some models of the series Bosch Classixx or Maxx the relay can be covered with an additional casing made of tin or dense plastic to protect it from dust and moisture. If you see only the wires going into the hole on the motor housing, then the protective cap must be carefully removed by prying it off with a screwdriver.
It is important to note that in two-compressor models Bosch there will be two such relays - one for each motor. They are located symmetrically or next to each other at the bottom of the rear panel. Do not confuse them with filter-driers, which look like small copper cylinders.
Signs of a faulty trigger mechanism
Before disassembling the equipment, you should make sure that the problem is in the relay. A typical symptom is the refrigerator turning on and off cyclically. The motor hums for a few seconds, a loud click is heard, and the unit goes silent. This indicates that starting winding does not receive the necessary impulse.
Another sign is the lack of cold in the chambers when the lights and fans are running (if any). The compressor may be hot to the touch, indicating that starting attempts have been unsuccessful. In such cases, the relay often has a melted housing or a characteristic burning smell.
- 🔊 A loud metallic click every 10-20 seconds of operation.
- 🔥 Intense heating of the compressor housing in the absence of cooling.
- 🚫 Complete refusal of the refrigerator to turn on even if it is working properly socket.
- 👃 The appearance of a smell of melted plastic in the area of the engine compartment.
Sometimes the malfunction is accompanied by knocking out plugs or circuit breakers in the electrical panel. This occurs if there is a short circuit of the contacts inside the relay. In such a situation, further attempts to turn on are strictly prohibited until the unit is replaced.
Step-by-step instructions for dismantling the relay
To carry out the work you will need a minimum set of tools: flat and Phillips screwdrivers, pliers and, possibly, a multimeter for testing. The dismantling process in refrigerators Bosch is standardized, but requires care.
First remove the back metal panel, if installed. In some models it is held on by screws, in others - by plastic latches. Open access to the compressor and visually inspect the condition of the wires and the relay itself.
☑️ Preparation for dismantling
Carefully disconnect the block with wires that goes to the relay. Usually it is fixed with a plastic clip that needs to be squeezed out. Then remove the relay itself from the compressor pins. It may fit tightly, so rock it slightly from side to side, avoiding jerking, so as not to damage the tubes.
If the relay is mounted on a metal frame, it must also be removed. Pay attention to the marking of the part, since it is Bosch important to use compatible analogues. Older models may have been equipped with relays from different manufacturers, such as Danfoss or Secop.
⚠️ Attention: When removing the relay, do not apply excessive force to the copper compressor tubes. They can easily be bent or broken, which will lead to freon leakage and expensive repairs.
Diagnostics and performance testing
After removing the device, it must be checked. A visual inspection often provides 50% of the information: melted contacts, blackened plastic or cracks indicate the need for replacement. However, external integrity does not guarantee serviceability.
For accurate diagnostics, use a multimeter in continuity mode. Check the resistance between the contacts. In good condition, it should be close to zero (for closed contacts) or infinity (for open contacts). Lack of response from the device indicates an internal break.
It is also worth checking the thermal protection, which is often built into the relay housing. It should “ring” when cold. If the circuit is open even when the relay is cold, it means that the thermal fuse has burned out and requires replacement along with the starting mechanism.
Is it possible to check the relay without a multimeter?
Theoretically, you can try to start the compressor directly, bypassing the relay, but this is dangerous and requires skills. A short-term supply of voltage to the starting winding can start the motor, but the risk of burning the winding or getting an electric shock is very high. It is better to use a tester.
The table below shows the main parameters for checking various types of relays found in technology Bosch.
| Relay type | Coil resistance | Thermal protection | External signs |
|---|---|---|---|
| Starting (PTC) | 20-40 Ohm | Closed (0 Ohm) | Case integrity |
| Electromagnetic | 10-15 Ohm | Closed (0 Ohm) | Core mobility |
| Faulty | Infinity | Open | Fusing, carbon deposits |
| Short circuit in the winding | 0 Ohm | Any | Smell burnt |
Replacement and installation of a new component
Selection of a new part is carried out strictly according to the marking of the old model or according to the model of the refrigerator Bosch. Universal relays exist, but they may not work correctly with a specific type of compressor, which will lead to rapid failure of the new element.
Installation is carried out in the reverse order of dismantling. Push the relay onto the compressor pins as far as it will go. Make sure it sits straight and doesn't wobble. Then connect the electrical block, checking the reliability of the fixation.
After assembly, do not rush to close the back panel. Plug in the refrigerator and listen. Startup should be smooth, without loud clicks or buzzing. If the motor is running smoothly, you can fix the panel and move the equipment to the wall.
Common mistakes during self-repair
One of the common mistakes is ignoring the cause relay failure. Often burnout occurs due to power surges or problems with the compressor itself. Installing a new relay without eliminating the root cause will lead to repeated failure in a short time.
Also, users often confuse the relay with a filter drier or thermostat. Visually they may look similar to the untrained eye, but functionally they are completely different units. Replacing a thermostat instead of a relay will not solve the problem of starting the motor.
- ❌ Installing a relay without checking the condition of the compressor windings.
- ❌ Using a part from another refrigerator model.
- ❌ Incomplete connection of the contact group, leading to sparking.
- ❌ Ignoring the condition of electrical wiring and sockets.
It is important to understand that if after replacing the relay the refrigerator behaves strangely again, the problem may be deeper. There may be a turn-to-turn short circuit in the engine or a coolant leak. In such cases, professional diagnostics are required.
⚠️ Attention: Technical characteristics and location of parts may vary slightly depending on the year of manufacture and the specific series of the Bosch refrigerator. Always check the diagram in the technical documentation of your device.
Prevention and extension of service life
To make the relay and compressor last longer, provide the refrigerator Bosch proper ventilation. The back wall should not lie close to the furniture; the distance should be at least 10 cm. Overheating of the motor is the main enemy of the starting equipment.
Regularly clean the rear grille of dust and animal hair. A dust “carpet” on the condenser and compressor impairs heat transfer, forcing the relay to operate in extreme temperature conditions. Simple vacuuming every six months will significantly reduce the load.
Use a voltage stabilizer if there are surges in your network. Sudden voltage changes often cause the combustion of not only the relay, but also the more expensive refrigerator control electronics. This is an inexpensive investment in the safety of equipment.
Does tilting the refrigerator affect the operation of the relay?
Yes, strong vibration or an incorrect tilt angle can disrupt the operation of the contacts inside the relay, especially the electromagnetic type. Make sure that the refrigerator is on a level floor and the legs are adjusted.
Is it possible to install a relay from another brand of refrigerator on a Bosch?
Theoretically, this is possible if the electrical parameters (current, voltage, compressor type) and mounting dimensions match. However, manufacturers use different connection schemes. Installing a non-original part may lead to incorrect operation of the protection and damage to the compressor. It is better to look for an analogue by catalog number.
How much does it cost to replace a relay in a service center?
The cost consists of the price of the part and the work of the technician. The relay itself is inexpensive, but a specialist visit and diagnostics can increase the total amount. Self-replacement saves up to 70% of costs if you are confident in your abilities and diagnosis.
Why does a new relay burn out immediately after installation?
This indicates a serious problem with the compressor (interturn short circuit, jamming) or critical problems with the electrical network in the house. The reason may also be incorrect installation or defective part of the new part. An in-depth diagnosis of the motor is required.
How to distinguish an original Bosch relay from a fake?
The original has clear markings, a manufacturer's logo (often Danfoss, Secop or Bosch itself), high-quality assembly without burrs and the smell of cheap plastic. Counterfeits are often made of fragile material and do not have detailed technical information on the case.