A sudden stop in the operation of refrigeration equipment often causes panic, especially if there is a large supply of food inside. In most cases, when the refrigerator Bosch stops cooling, but the light is on inside, users immediately suspect a failure. This is the heart of the system, and its failure is truly critical, but one should not rush to conclusions. Often the problem lies in simpler elements, such as a start relay or thermostat, the replacement of which is much cheaper. motor-compressor. This is the heart of the system, and its failure is truly critical, but one should not rush to conclusions. Often the problem lies in simpler elements, such as a start relay or thermostat, which are much cheaper to replace.
Before proceeding with complex technical manipulations, it is necessary to carry out primary visual and auditory diagnostics. If you hear a characteristic hum that ends abruptly with a click, or the unit is silent, despite the cord being plugged in, this indicates a specific range of malfunctions. Checking the compressor requires care and compliance with safety precautions, since the work involves high-voltage electric current.
In this article We will analyze in detail the algorithm of actions that will allow you to determine whether your “engine” is alive Bosch or it needs to be changed. We'll look at methods for using a multimeter, testing windings for short circuits, and analyzing the state of a start-up relay. Understanding these processes will help you make an informed decision: call a technician for complex repairs or try to fix the problem yourself.
⚠️ Attention: Before starting any work on diagnosing electrical appliances, be sure to disconnect the device from the power supply. Working with capacitors and energized windings is deadly.
Initial assessment of the condition and external signs
The diagnosis should begin by analyzing the behavior of the refrigerator. If the unit Bosch turns on, runs for a few minutes, and then turns off with a loud click, this is a classic symptom of an overload or faulty starter. In such a situation compressor it may be serviceable, but cannot start due to problems with the starting winding or jamming of the piston group. It is also worth paying attention to the temperature of the case: if the motor is excessively hot to the touch immediately after trying to start, this is a bad sign.
The opposite situation, when the refrigerator is absolutely silent, also requires checking. Make sure that the problem is not a lack of power at the outlet or a damaged power cord. If the indicators are on, the fan (if the model has one) may work, but the engine will not start. In models with inverter compressor silence may mean an electronic error blocking the start, while in classic linear models it is most often an open circuit or a burnt-out relay.
It is important to listen to the sounds made by the unit. A uniform hum followed by silence is a normal operating cycle. However, intermittent sounds, grinding or vibration radiating into the housing indicate mechanical wear. If you observe such signs, further use may lead to complete destruction of the internal components. In this case an attempt to turn it on multiple times can finally finish off the electric motor that is still working..
Dismantling and access to the technical compartment
To carry out high-quality diagnostics, it is necessary to gain direct access to the compressor. In refrigerators Bosch it is usually located in the lower rear part of the case. You will need to remove the protective panel, which may be secured with latches or screws. Be careful not to damage the plastic clips, which become brittle over time. After removing the cover, you will see a black cylindrical compressor tank, a capacitor grille and a start relay.
First, inspect the wires going to the terminal box. The absence of traces of burning, melting of insulation or oxidation of contacts is a good sign. If you see black spots or smell burnt plastic, the problem most likely lies in start relay or inter-turn short circuit of the windings. Visual inspection often allows you to immediately localize the fault area without resorting to tools.
☑️ Preparation for diagnostics
Next you need to remove the starting relay. It fits directly onto the compressor terminals and is secured with a bracket or latches. Remove it carefully, without jerking, so as not to break the suitable wires. There is usually an arrow on the relay body indicating the correct position (up/down), remember this before removing. Inside the relay there is a starting coil and a posistor (or mechanical switch), which are often the first to fail.
Checking the serviceability of the starting relay
The starting relay is the key element responsible for starting the engine. In refrigerators Bosch relays with a posistor are most often used. The principle of their operation is simple: when voltage is applied, the posistor heats up and opens the starting winding circuit. If it burns out, no current will flow to the starting winding, and the compressor will not be able to overcome the inertia of rest. You can check it visually (for cracks) and using a multimeter in continuity mode.
Take the relay in your hand and shake it. If a clear knocking or ringing sound is heard inside, like from a broken stone, it means the posistor is destroyed. This is a 100% sign of a malfunction. Even if visual integrity is preserved, the absence of resistance on the contacts when checked by a tester indicates the need for replacement. The cost of this part is low, and replacing it often solves the problem of a “non-working” refrigerator.
⚠️ Attention: Do not try to repair the start relay by gluing or cleaning the contacts if the posistor is damaged. This is a temporary measure that can lead to a fire due to overheating.
Also check the contacts that are inserted into the compressor terminals. They should be clean and elastic. Oxidation causes voltage drop and inefficient engine operation. If the contacts are burnt, they can be carefully cleaned with fine sandpaper, but it is better to replace the entire relay. After checking the relay, if it is working properly, we move on to a more complex procedure - diagnostics of the windings the motor itself.
How does a posistor work in a relay?
A posistor is a semiconductor element whose resistance increases sharply when heated. When the refrigerator is turned on, it is cold and passes current to the starting winding, helping the rotor to spin. After a few seconds, it heats up from the passing current, its resistance increases, and it turns off the starting winding, leaving only the main winding to work. If this cycle is broken, the compressor hums, but does not start.
Diagnostics of windings with a multimeter
This is the most reliable way to determine the technical condition of the electrical part of the engine. To work, you will need a multimeter switched to resistance measurement mode (Ohm). On the compressor body Bosch there are three terminals, usually covered with a plastic cover. When you remove the cover, you will see three contacts forming a triangle. They correspond to the starting, operating winding and common wire.
The testing process consists of measuring the resistance between each pair of contacts. Normal resistance values depend on the engine power, but usually lie within the following limits: between the working and common windings - 10-20 Ohms, between the starting and common windings - 20-40 Ohms, between the working and starting windings - the sum of the two previous values. If the device shows infinity (open circuit) or zero (short circuit), the compressor is faulty.
| Pair of contacts | Normal resistance (Ohm) | Fault symptom | Probable cause |
|---|---|---|---|
| Working - General | 10 - 25 Ohm | ∞ (Infinity) | Breakage of the working winding |
| Starting - General | 20 - 45 Ohm | 0 Ohm | Short circuit |
| Working - Starting | Sum of the two above | Unstable readings | Poor contact or breakdown |
| Any pair - Housing | ∞ (Infinity) | Any value | Insulation breakdown on the housing |
Pay special attention to checking for “breakdown” of the housing. Press one multimeter probe to any of the three contacts, and touch the other unpainted part of the metal body of the compressor (you can first clean a small area). The device should show infinity. If the arrow deviates or the digital display shows any values, it means that the insulation of the windings is broken. Operating such a unit is strictly prohibitedas this may result in an electric shock.
Analysis of mechanical faults and jamming
Electrical serviceability of the windings does not guarantee the operation of the compressor. The mechanical part - the piston group and valves - is also subject to wear. If the electrical parameters are normal, the relay is working properly, but the engine does not start or makes a loud metallic clanging noise, it is likely seized. This often happens after a long period of inactivity or due to the exhaustion of the life of rubbing parts.
There is a “wedging” method, when increased voltage is supplied to the compressor or it is switched on directly for a short time, bypassing the relay. However, for domestic conditions and inexperienced users, this method not recommended. It requires special equipment (transformer) and skills, since incorrect actions can lead to an explosion of the windings or a fire. In apartment conditions, it is safer to replace the entire assembly.
Another cause of mechanical failure may be loss of compression. In this case, the motor runs, hums, but does not create the necessary pressure in the system. You can check this by disconnecting the capillary tube at the outlet (flaring is required). If there is no strong flow of air or freon coming from the tube when the engine is running, it means the valves are worn out or damaged. This requires professional repairs with evacuation of the system and charging of refrigerant.
⚠️ Attention: Opening the refrigeration circuit (depressurization) without subsequent evacuation and charging with freon will lead to moisture getting inside the system. The moisture will freeze in the capillary and completely damage the refrigerator.
Specifics of Bosch inverter compressors
Modern models Bosch are often equipped with inverter compressors that work according to a fundamentally different scheme. They do not have the classic starting relay and posistor. Starting and speed control is carried out by an electronic module (inverter). Diagnosing such systems with a conventional multimeter is difficult, since the resistance of the windings can be very low (less than 10 ohms), and the tester may show a short circuit, although this is normal.
To check the inverter motor, it is necessary to measure the resistance between the contacts. In three-phase motors, the resistance between all three pairs of contacts must be the same. If the values are very different or show a break, the engine is faulty. However, most often in inverter systems, the control unit itself fails, and not the mechanical part of the compressor.
If your refrigerator Bosch with the inverter does not start, pay attention to the error code on the display (if there is one) or to the blinking indicators. Often the self-diagnosis system itself indicates a problem with the compressor or control module. In such cases, self-repair is limited to replacing visible damage to the wiring; in-depth diagnostics require contacting a service center.
Frequently asked questions and answers
Is it possible to replace a compressor with an analogue from another manufacturer?
Technically, this is possible if the dimensions, power, type of refrigerant and oil volume are the same. However, for refrigerators Bosch it is strongly recommended to use original spare parts or certified analogs (for example, Secop or Danfoss), since incompatibility can lead to rapid failure of the new part.
Why does a new compressor heat up to 90 degrees?
High case temperature (up to 80-90°C) is the normal operating temperature for many compressor models, especially under high load or in a hot room. If there is no burning smell and the unit is cooling, this is not a malfunction. However, if the temperature rises quickly and a shutdown occurs, check the cleanliness of the condenser at the back.
How much does it cost to replace a compressor in a service?
The cost consists of the price of the unit itself and the work of the technician. Depending on the model Bosch and region, the price may vary. The exact amount can only be found out after diagnostics, since it may be necessary to replace the filter-drier and refill with freon.
Is it possible to restore a compressor if it is jammed?
There are methods of “wedging” by increasing the voltage or mechanical action, but they have a low success rate and high risk. In factory conditions, such engines are not repaired, but replaced. For a home mechanic, trying to revive a jammed motor is a lottery with a high chance of final breakdown.