Sudden stoppage of the refrigerator Bosch often causes panic, especially if a large supply of food is stored in the chambers. However, in many cases, the cause of the breakdown is not the compressor or freon leak, but a much cheaper and more accessible part - the start relay. This small element is responsible for starting the engine and its operation in normal mode, and its failure is one of the most common problems in household appliances.
Self-diagnosis of this unit allows you to save a significant amount on calling a technician, since the verification process is quite simple and does not require deep knowledge in electrical engineering. All you need is a minimal set of tools and a basic understanding of how a refrigerator's electrical circuit works. If you notice that the engine hums but does not start, or hear characteristic clicks, the problem most likely lies in this component.
Before starting disassembly, it is important to make sure that the work is safe. Any manipulations with electrical components should be carried out only after completely disconnecting the device from the network. Ignoring this rule can lead not only to damage to the electronics, but also to electric shock, which is unacceptable during home repairs.
⚠️ Attention: Before starting any diagnostic work, be sure to unplug the refrigerator from the outlet. The residual voltage in the capacitors may persist for several minutes, so let the equipment stand unplugged for about 10-15 minutes before removing the back panel.
To begin diagnostics, you will need to determine the exact model of your unit, since the relay design may vary depending on the series Bosch. Older models can be equipped with induction starters, while modern ones are often equipped with posistor elements. Understanding the type of device will help you choose the right testing method and avoid mistakes when assessing the condition of the part.
Signs of a faulty starting relay
Symptoms of a faulty starting mechanism are often pronounced, which allows you to quickly localize the problem. Owners of refrigerators Bosch most often encounter a situation where the compressor tries to start, makes a hum, but after a few seconds a click is heard and the motor goes silent. This cycle can be repeated at certain intervals until the thermal relay turns off the power completely to protect the engine from overheating.
Another characteristic sign is the absence of cold in the chambers when the light is working and the control panel is working. If you hear the motor humming, but there is no vibration or the characteristic sound of the compressor operating, this is a good signal to check the starting unit. In some cases, the malfunction is accompanied by a specific smell of burning or melted plastic in the area of the engine compartment.
- 🔊 The compressor hums for 5-10 seconds, then a click is heard and silence sets in.
- ❄️ The temperature in the refrigerator and freezer compartments rises, food begins to deteriorate.
- ⚡ The automatic switch in the electrical panel trips when you try to turn on the refrigerator.
- 🔥 The appearance of a burning smell or visible traces of melting on the relay body.
Sometimes the refrigerator may behave strangely, turning on and off in a chaotic manner. This may indicate that the contacts inside the relay are burnt, but have not yet completely lost conductivity. In this state, the part creates increased resistance, which leads to overheating of the connections and eventual breakdown of the compressor if the element is not replaced in time.
Removing the relay: step-by-step instructions
The process of removing the start relay from refrigerators Bosch is standardized, but requires care. To access the unit, you need to move the refrigerator away from the wall and remove the rear metal panel covering the engine compartment. Usually it is attached to several screws around the perimeter, which are easily unscrewed with a Phillips screwdriver.
After removing the panel, you will see the compressor - a black metal “cylinder” at the bottom of the case. On the side rod of the motor there is a plastic box, which is the required relay. In modern models Bosch it is often closed with an additional protective casing or fixed with a metal bracket, which must be carefully bent or unscrewed.
☑️ Preparation for dismantling
The most important thing when dismantling is to correctly remove the part from the compressor contacts. Do not pull on the wires as you may damage the insulation or tear off the terminals. It is necessary to grab the relay body, rocking it from side to side, and at the same time pull down. In some cases, the plastic may dry out from time and temperature, then carefully using a flat-head screwdriver to pry up the edges will help.
⚠️ Attention: There may be condensation or traces of oil inside the relay. When removing, hold the part with the holes facing down so that liquid does not get on the wire insulation or inside the compressor housing, which could cause a short circuit.
After you have removed the relay from the contacts, carefully inspect the wires going to it. It often happens that the problem lies not in the part itself, but in oxidized or burnt contacts on the terminals. If you see traces of severe corrosion or melting on the wires, their stripping may not be sufficient - it is better to replace the entire terminal block.
Visual inspection and initial diagnostics
The first stage of testing does not require the use of measuring instruments. Carefully inspect the relay housing for cracks, chips, or signs of thermal damage. If the plastic is blackened or warped, this is an indication of overheating caused by a short circuit or overcurrent. In this case, the part definitely needs to be replaced.
Shake the relay near your ear. If you hear knocking or rattling inside, this is a bad sign. When in good condition, the internal components are tightly secured. The presence of extraneous sounds indicates that the mechanical part is destroyed, the contacts could have shifted, and normal switching of the circuit is impossible.
What is inside the relay?
Inside the plastic case there is a coil, a movable core, a contact group and, in some models, a posistor (ceramic element). When voltage is applied, the coil creates a magnetic field that draws in the core and closes the contacts, starting the motor winding. The posistor heats up and opens the starting winding after gaining speed.
Pay special attention to the contact groups. If it is possible to carefully open the case (which can be difficult without causing damage), inspect the condition of the “spots” of the contacts. The presence of carbon deposits, black spots or pits on the metal surface indicates sparking. Light carbon deposits can be cleaned with fine sandpaper, but if the metal is deeply burnt, it is better to replace the relay.
For refrigerators Bosch with inverter compressors the situation is different. In such models, the starting relay is often built into an electronic control unit located directly on the motor housing. It is more difficult to check it visually, and often requires diagnosing the electronic module itself, and not just the mechanical switch.
Checking with a multimeter: electrical diagram
The most accurate diagnostic method is to test the circuit using a multimeter. Switch the device to resistance measurement mode (Ohm) or circuit continuity test mode (audible mode). This will allow you to determine whether there is a break in the windings or sticking contacts.
First check the inductor. Place the multimeter probes on the corresponding relay contacts. The resistance must be within a certain range, usually from 30 to 200 ohms, depending on the model. If the device shows one (infinity), it means there is a break in the winding and the relay does not work. If zero, a short circuit of the turns has occurred.
Next, the mechanical part is checked. In the normal position (the relay lies on the table), the contacts of the starting winding should be open. The multimeter should show an open circuit. If you turn the relay over or press the rod (if accessible), the contacts should close and the device will beep. Lack of reaction indicates jamming of the mechanism or severe oxidation of the contacts.
For posistor relays, it is important to check the ceramic element itself. It must have resistance when cold. However, the main test of the posistor occurs under voltage, which is dangerous to do at home. Therefore, if a visual inspection and coil testing do not reveal problems, but the refrigerator does not start, the posistor is often changed preventively due to its low cost.
| Type of check | Good condition | Fault | Action |
|---|---|---|---|
| Visual inspection | Clean body, no smell | Fusing, burning, cracks | Part replacement |
| Coil continuity test | Resistance 30-200 Ohm | Infinity or 0 Ohm | Replacement of part |
| Checking contacts | Short circuit when turning over | No reaction, constant ringing | Cleaning or replacement |
| Posistor | There is resistance | Circuit break in cold | Replacement of part |
Selecting a replacement and features of Bosch models
When purchasing a new relay for a refrigerator Bosch it is critically important to know the exact article number of the original part or its complete analogue. Universal relays exist, but they may not work correctly with a specific type of compressor, which will lead to rapid failure of a new part or the motor itself.
Pay attention to the number of contacts and their location. Relays can have 2, 3 or more terminals. The orientation of the connection is also important: some models are designed to be installed with the stem down, others - up. Incorrect installation of a mechanical relay will result in it simply not turning on or off.
⚠️ Attention: Do not use relays from other brands (for example, Indesit or Atlant) without checking the electrical characteristics. Current parameters and response times may differ, which is dangerous for the compressor Bosch.
If you have not found an original spare part, look for cross-numbers (analogs). Electronics manufacturers often mark relays with codes that may be the same across different brands. For example, relay PTC series can be interchangeable if the coil voltage and operating current are the same.
Installing a new relay and testing
The process of installing a new part is a mirror image of dismantling. Make sure the contacts on the compressor are clean and dry. Carefully slide the relay onto the compressor rod until it clicks or makes a tight fit. Do not use excessive force to avoid damaging the ceramic motor terminals.
Connect the wires to the appropriate terminals. It is extremely important here not to confuse the polarity and purpose of the wires. If you did not photograph the circuit before disassembly, refer to the documentation or color coding of the wires, which is usually standard for Bosch: phase, neutral and ground.
After assembling the entire structure, do not rush to close the back panel. Plug in the refrigerator and listen. Startup should occur within 1-3 seconds. The motor should run smoothly, without humming or vibration. After 5-10 minutes, check whether the condenser (grid at the back) or the side walls of the refrigerator has begun to heat up - this is a sign that the operating cycle has begun.
- ✅ The relay sits tightly on the compressor contacts.
- ✅ All wires are connected according to the diagram and securely fixed.
- ✅ When turned on you can hear the engine start confidently without humming.
- ✅ After 15 minutes of operation, the compressor is warm, and cold begins to appear in the chambers.
If after replacing the relay the situation has not changed and the compressor hums and clicks again, the problem may be deeper. Perhaps the compressor itself is faulty (interturn short circuit of the windings) or there are problems with the wiring. In this case, self-repair can be dangerous, and it is better to contact a service center.
Is it possible to repair an old relay rather than buy a new one?
Theoretically, if the problem is only burnt contacts, they can be cleaned. However, the resource for such repairs is extremely short. The factory contact plating (often silver) is damaged and the copper will quickly oxidize again. Considering the low cost of new relays, repairing the old one is economically impractical and risky.
Why does the relay burn out on a Bosch refrigerator?
The main reasons: power surges, rare switching on of the refrigerator (oil solidification in the compressor), frequent opening of the door (load on the motor) or natural wear of the contacts. Also, the reason may be a malfunction of the compressor itself, which consumes too much current when starting.
How much does it cost to replace a relay in the service?
The cost consists of the price of the part (from 500 to 2000 rubles depending on the model) and the work of the technician. In service centers, the cost of visiting and diagnostics can be a significant part of the amount. Replacing it yourself allows you to save on work, since technically it is a simple operation.
Is it dangerous to operate a refrigerator with a faulty relay?
Yes, it is dangerous. Constant attempts to start create a huge load on the compressor windings, which can lead to their burnout. Replacing a compressor costs 3-4 times more than replacing a relay. In addition, overheating of the wiring can cause a fire.