How to independently check the temperature sensor in a Bosch refrigerator: 5 working methods

The temperature sensor (thermistor) in the refrigerator Bosch is a small but critical element that is responsible for correct operation of the entire cooling system. If it malfunctions or begins to give incorrect readings, the refrigerator may stop freezing, freeze food too much, or, conversely, not cool enough. In most cases, a sensor malfunction leads to error code on the display (for example, E01, E02 or E24 in models with electronic control), but sometimes the problem manifests itself indirectly - through unstable temperature or constant operation of the compressor.

You can check the temperature sensor in the refrigerator Bosch you can do it yourself, without resorting to the services of a technician. This does not always require special tools - in some cases, a careful inspection and basic knowledge of how the equipment works is sufficient. However, if you decide to use a multimeter, it is important to understand which values ​​are considered normal and which indicate failure. In this article we will examine 5 diagnostic methodsincluding testing without instruments, resistance testing and visual inspection, and also tell you how to distinguish a faulty sensor from problems with the control board or compressor.

Signs of a faulty temperature sensor in a Bosch refrigerator

Before you start checking, you need to make sure that the problem is really related to the sensor. Errors in its operation manifest themselves in different ways, but there are several characteristic symptomsthat should alert you:

• 🔴 Refrigerator does not turn off or, conversely, turns on too rarely (the compressor works without stopping or with large pauses).
• ❄️ In the freezer a thick layer of ice has formed, although the mode No Frost is on.
• 🌡️ The temperature in the chambers does not correspond to the set one (for example, in the refrigerator compartment +10°C instead of +4°C).
• 🚨 On the display appear errorstemperature-related: E01, E02, E24, F02 (depending on the model).
• 🔄 Refrigerator spontaneously reboots or resets settings.

It is important to consider that similar symptoms can occur with other malfunctions, for example, when freon leak, a compressor breakdown or a malfunction of the electronic board. Therefore, before replacing the sensor, it is recommended to carry out comprehensive diagnostics. If your refrigerator Bosch belongs to the KGE39..., KGN39... or KAN9...series, the likelihood of problems with the sensor is higher - in these models thermistors more often fail due to design features.

⚠️ Attention: If the refrigerator is on guarantee, do not disassemble it yourself! Doing so may void your warranty. Contact the service center Bosch.

Where is the temperature sensor in the Bosch refrigerator

In refrigerators Bosch temperature sensors (thermistors) are installed in different places depending on the model and type cooling systems. In most cases, they can be found:

• 📍 In the refrigerator compartment: usually attached to the back wall, next to the evaporator or on the top panel (in models with No Frost).
• ❄️ In freezer: located on the evaporator or inside the air duct (if there is a ventilation system).
• 🔄 Environmental sensor: in some models (for example, Bosch KIN86...) it is installed outside, on the refrigerator body, to adjust the operation of the compressor depending on the room temperature.

To accurately determine the location of the sensor in your model, you can use operating instructions or find the diagram on the official website Bosch. If the documentation is lost, be guided by the following signs:

• 🔍 The sensor looks like a small one plastic cylinder with two wires, often wrapped in a heat-shrinkable tube.
• 📏 The size usually does not exceed 2–3 cm in length.
• 🔌 The wires from the sensor go to control board (it is located on the back wall of the refrigerator, under the lid).

In models with a system No Frost (for example, Bosch KGN39XW20) there can be several sensors: separately for the refrigerator and freezer compartments, as well as for monitoring operation fan. If you are not sure which sensor has failed, you will have to check each one in turn.

What does the temperature sensor look like in a Bosch refrigerator?

Usually it is a small cylindrical or oval element with a diameter of 5-10 mm, wrapped in a protective sheath. The color can vary from black to white. The sensor is connected to two thin wires (red. and white or black and white), which are connected to the connector on the control board. In some models, the sensor is mounted on a clip or tape, in others it is inserted into a special groove on the evaporator.

Preparation for testing: tools and safety measures

Before you begin diagnostics, you need to prepare tools and ensure safety:

• 🔧 Screwdriver (cross or flat, depending on the cover fastenings).
• 📊 Multimeter (to measure the resistance of the sensor).
• 🧊 Thermometer (preferably electronic, to check the real temperature in camera).
• 🧤 Gloves (to avoid leaving fingerprints on the internal surfaces).
• 📸 Smartphone (for photographing the location of the wires before disconnecting).

Also follow the following safety rules:

• ⚡ Unplug the refrigerator before starting work! This will prevent electric shock and reset.
• 🕒 Let the refrigerator sit for 10-15 minutes after disconnecting, so that the capacitors are discharged.
• 🚫 Do not touch the evaporator with your bare hands —it may be sharp or cold.
• 🔄 Do not mix up the wires when connecting the sensor back - this can lead to a short circuit.

If you do not have a multimeter, you can do without it, but the diagnostic accuracy will be lower. In this case, you will have to rely on indirect signs and visual inspection for models Bosch with an electronic display. (for example, KIV38X...) is useful before checking write down the error code, if it appears, this will help narrow down the range of possible problems.

⚠️ Attention: If your refrigerator is connected to the system Home Connect (smart home), before turning off the power, check whether the temperature settings are connected to external devices. In some cases, resetting may lead to loss of synchronization.

Method 1: Checking the temperature sensor without a multimeter

If there are no measuring instruments at hand, you can try to diagnose the sensor malfunction indirect methods. This method is less accurate, but will help identify obvious problems.

Sequence of actions:

1. Disconnect the refrigerator from network and let it stand for 1-2 hours so that the temperature in the chambers is equal to room temperature.
2. Turn the refrigerator back on and set the minimum temperature (for example, +2°C in the refrigerator compartment).
3. Check the operation of the compressor:
   • If it is does not turn on at all the problem may be sensor, control board or compressor.
   • If it works without stopping more than 30 minutes, the sensor most likely transmits incorrect data (for example, it shows a high temperature, although the chamber is cold).

Measure the real temperature in the chamber using a separate thermometer. If it differs greatly from the set one (for example, +10°C instead of +4°C), this indirectly confirms that the sensor is faulty.

Also pay attention to freezing of the evaporator:

• If on it no ice, but the refrigerator does not cool - the sensor may show falsely high values.
• If there is ice increases too much quickly the sensor, on the contrary, lowers the temperature, causing the compressor to work longer.

This method does not provide a 100% guarantee, but it helps to narrow down the range of possible faults. If suspicions about the sensor are confirmed, proceed to more accurate diagnostics with a multimeter.

Method 2: Checking the sensor with a multimeter (step-by-step instructions)

The most reliable diagnostic method is measuring the resistance of the sensor at different temperatures. To do this, you will need a multimeter with a resistance measurement function (ohmmeter).

Step-by-step instructions:

1. Remove the sensor:
   • Usually it is attached to latches or tape. Carefully disconnect it from the evaporator or wall.
   • Disconnect the connector with wires from the control board (located on the back wall of the refrigerator under the lid).
2. Connect the multimeter:
   • Set the resistance measurement mode (range 20 kOhm).
   • Connect the probes to the sensor contacts (polarity is not important).

Measure the resistance:

• When room temperature (+20...+25°C) the resistance of a working sensor should be within the limits 4–7 kOhm (exact values depend on the model, see the table below).
• Place the sensor in a glass with ice water (0°C) - resistance should increase to 25–32 kOhm.
• Heat the sensor with your hand or a hairdryer (up to +40...+50°C) - the resistance should drop to 1–3 kOhm.

If the resistance does not change when the temperature or its value changes exceeds the specified limits, the sensor is faulty and requires replacement. Also pay attention to breaks or short circuits:

• If the multimeter shows infinity (OL) an open circuit in the sensor circuit.
• If the resistance close to 0 Ohm is a short circuit.

Temperature (°C)	Resistance of a working sensor (kOhm)	Note
-20	40–50	Typical for a freezer
0	25–32	Ice or ice water
+20	4–7	Room temperature
+40	1–2	Heating by hand or hairdryer

In models Bosch series KAD9... and KAN9... sensors may have a nonlinear characteristic, so for accurate diagnosis check the technical documentation of the specific model.

Method 3: Checking the voltage on the control board

If the sensor shows adequate resistance values, but the refrigerator still does not work correctly, the problem may lie. in circuits between the sensor and the control board. In this case, you need to check whether the signal reaches the electronic module.

How to check:

1. Connect the sensor back to board, but do not install it in place.
2. Plug in the refrigerator.
3. Switch the multimeter to constant voltage (DC) measurement mode and connect the probes to the connector contacts on the board where the sensor fits.
4. Measure the voltage:
   • It should be within 3–5 V (the exact values depend on the model).
   • If the voltage absent (0 V) the problem is in the board or a broken wire.
   • If the voltage exceeds 5 V the electronic module may malfunction.

Also pay attention to the state of the contacts:

• 🔍 If they are oxidized or dirty - clean them with alcohol or an eraser.
• 🔌 If the connector loose - this may lead to signal loss. Try to bend it carefully. contacts.

If the voltage on the board is normal, but the refrigerator still does not work correctly, perhaps the problem is electronic firmware. moduleIn this case, resetting the settings or flashing it can help (it is better to entrust this to a specialist).

⚠️ Attention: Working with the control board requires caution! Do not touch its elements with wet hands and do not use metal tools that can cause a short circuit.

Method 4: Diagnostics through the service menu (for models with a display)

Refrigerators Bosch with electronic control (for example, KIN86AF30, KGN39XL30) have hidden service. menuthrough which you can check sensor readings in real time. This allows you to compare the actual temperature with what the system “sees.”

How to enter the service menu:

1. Unplug the refrigerator for 10 seconds, then turn it back on.
2. During 5 seconds after turning on, press and hold the button Super (or Eco, depending on the model) for 10 seconds.
3. The service menu will appear on the display (usually displayed t0, t1, t2 etc. - these are temperatures from different sensors).
4. Compare the readings:
   • t0 or tA — temperature in the refrigerator compartment.
   • t1 or tB —temperature in the freezer compartment.
   • t2 —ambient temperature (if there is an external sensor).

If the values differ greatly from the real ones (for example, t0 = -10°C, although the camera is +20°C), the sensor is faulty.

To exit the service menu, press and hold the same button (Super or Eco) for 5 seconds.

In some models (for example, Bosch KIV87VS30), the service menu may have additional parameters, such as:

• d0, d1 — door status (open/closed).
• F0–F3 —error codes related to the fan, compressor or sensors.

⚠️ Attention: Do not change the values in the service menu if you are not sure of their purpose! This may lead to a malfunction of the refrigerator.

Method 5: Replacing the temperature sensor (if the check confirmed the malfunction)

If the diagnostics showed that the sensor is faulty, it must be replaced. In most cases, this can be done independently, without the help of a technician.

Step-by-step replacement instructions:

1. Buy a new sensor:
   • For refrigerators Bosch Original sensors with article numbers are suitable 00643439, 00643440, 00643441 (depending on the model).
   • You can use analogues, but make sure that their resistance corresponds to the table above.
2. Disconnect the refrigerator from the mains and remove the back cover (if the sensor is located inside the case).
3. Disconnect the old sensor:
   • Carefully disconnect the connector from the control board.
   • Remove the sensor from the mount (it can be glued or fixed with a clip).
4. Install a new sensor:
   • Fix it in the same place where the old one was.
   • Connect the connector to the board (watch the polarity if the wires are different color).

Check the operation of the refrigerator:

• Plug it in and set the desired temperature.
• Make sure that the compressor turns on and off as normal.

If the problem persists after replacing the sensor, it may be is faulty control board or there are other breakdowns (for example, freon leakage). In this case, it is recommended to contact a service center.

Cost of replacing the sensor:

• 💰 On your own: 500–1500 ₽ (sensor price) + time.
• 💼 In the service center: 2000–4000 ₽ (including the work of a technician).

Frequently asked questions about temperature sensors in refrigerators Bosch

🔹 Is it possible to repair the temperature sensor, or just replace it?

The temperature sensor (thermistor) is irreparable element. If it fails, it can only be replaced. Attempts to repair it (e.g., by soldering) usually lead to repeated failures.

🔹 How to distinguish a sensor failure from a control board failure?

If the sensor shows the correct resistance when tested with a multimeter, but the refrigerator does not work correctly, the problem is most likely board The following may also indicate a board malfunction:

• Lack of voltage at the sensor connector.
• Error codes not related to temperature (for example, E03 a problem with the fan).
• The refrigerator does not respond to pressing buttons.

In this case, diagnostics of the electronic module is required.

🔹 How many temperature sensors are there in a Bosch refrigerator?

The number of sensors depends on the model:

• In simple refrigerators (for example, Bosch KGN33...) — 1–2 sensors (for refrigerator and freezer compartments).
• In models with No Frost (for example, Bosch KAN92...) — 3–4 sensors (additionally for fan and environment).
• In Side-by-Side (for example, Bosch KAS96...) - up to 5 sensors.

The exact number is indicated in the diagram of your model.

🔹 What to do if, after replacing the sensor, the refrigerator still does not work?

Possible reasons:

• 🔌 Incorrect connection —check the polarity and reliability of the contacts.
• 🖥️ Control board failure —try resetting the settings (turn off the refrigerator for 10 minutes).
• ❄️ Freon leak —if the compressor works but does not cool, call a technician.
• 🔄 The new sensor is faulty —check it with a multimeter.

If the problem is not solved, contact the service.

🔹 Is it possible to use a sensor from another Bosch model?

Theoretically, yes, but only if:

• 📊 Resistance at the same temperature matches (see table above).
• 🔌 The connector fits to the control board.
• 📏 The physical dimensions allow you to install the sensor in place.

It is better to use an original spare part or a certified analogue.