Tacho Sensor (tachogenerator, Hall sensor) in Bosch washer (check and replace)

Have you noticed that laundry is not pressed well? Then it’s time to find out what is tachogenerator in a washing machine, how it works and what to do if the part is faulty. After all, its main task is to determine and increase the speed of the engine rotation.

Check and replace Tacho Sensor in Bosch washing machine
Check and replace Tacho Sensor in Bosch washer

The device is also called a Hall sensor in honor of its inventor.

The principle of the device operation

The Hall sensor is a small coil. When the motor rotates, a voltage is generated inside the coil under the action of a magnet. Depending on the speed of the electric motor’s rotation, it changes. By measuring the voltage, the sensor sends a message to the main module.

Where is the device installed in the Bosch washing machine? Of course, the part is located on the shaft of the electric motor. It allows performing the specified functions.

Diagnostics of the sensor malfunction

How can an ordinary user understand that there is a failure of the Hall sensor? External symptoms:

  1. The machine changes the speed of the drum rotation too abruptly.
  2. An insufficient number of revolutions for high-quality spinning of laundry.
  3. During washing, the drum rotates faster than expected.

But before you diagnose a breakdown, you need to know how to check the tachogenerator in an appliance. To do this, you have to remove the washing machine engine, so first eliminate the most likely problems:

  • Look at the control panel. Find the spinning button there and check it. Perhaps it is damaged and can’t be pushed the right way, which causes the malfunction.
  • Reboot the washing machine. Disconnect it from the mains for 15-20 minutes and then turn it on. If nothing changes, you need to check the tachogenerator.

Working process

Let’s start with the washing machine disassembly:

  1. Disconnect the machine from the mains and the communications.
  2. Remove all screws on the perimeter of the back panel.
  3. Remove it and leave aside.
  4. Now remove the drive belt.
  5. Pull it on yourself while scrolling the pulley.

Start dismantling the motor as follows:

  • Mark the wires leading to the motor to carry out a correct connection later.
  • Unscrew the bolts holding the engine. Pushing the motor back and forth, get it from the body.

Now inspect the Hall sensor in the washing machine. As a result of strong vibrations, its fastening could weaken, or the contacts went off. In this case, you need to reconnect and tighten the fastening bolt.

If everything is in order, you need to check the resistance of the appliance’s tachogenerator. There are two ways to do this:

  1. Set the tester to the resistance measurement mode. Unplug the wire connectors and remove them from the sensor contacts. When attaching the tester probes to the contacts, check the resistance value. In normal operation, the resistance of the device should be around 60-70 ohms.
  2. Now switch the voltage tester. You need to understand whether the device produces a current or not. If it works, then the tacho generator is working. To check, attach the tester to the sensor contacts while rotating the motor by your hand. If the figures change (about 0.2 Volts), then the part works.

Be sure to check the integrity of the wiring. Actually, the tachogenerator is rarely subjected to breakdowns. Perhaps the cause of the malfunction is in the control board. In this case, it is better to contact the service center.

How to replace the Tacho sensor in a washing machine

First, you need to remove the sensor from the washing machine. To do this, you first need to get rid of the connectors of the sensor if you haven’t already done so. Pull out the connectors, fixed in the common pads. Use a thin slotted screwdriver.

Then it is necessary to remove the cover of the pick-up device, which usually latches into place. Covers can be made of metal or plastic. Also, the lid can go along with the tachogenerator and is fastened with bolts. Unscrew the bolts that bolster the tackle and remove it.

Perform assembly in the reverse order.

Author: David Hoover