Error E21 in a Bosch washing machine

Sometimes users encounter this problem: the machine is turned on and the desired cycle is started, but after a while the drum stops and the washing machine freezes. The error code E21 appears on the display.

What does the E21 error code in a Bosch washing machine mean? How is the code deciphered? Which components of the washing machine need to be checked? Let's delve into the details.

Decoding the code

All modern Bosch washing machines are equipped with an automatic self-diagnostic system. Having detected a malfunction, the machine immediately displays the corresponding error code on the display. Washing machines without a display notify the user of a problem by flashing indicators on the control panel.

Which dashboard indicators light up depends on the washing machine model. For example:

• on Bosch Classic, code E21 corresponds to the flashing of the “Rinse” light;
• On Bosch Maxx 4, the “Ready for washing” and “Complete of cycle” LEDs will indicate a problem; they will flash simultaneously;
• Bosch Maxx 5, 6 and 7 will indicate error E21 by flashing the “Spin” and “Rinse” indicators.

You can find a breakdown of all possible errors in the instructions for your Bosch washing machine.

If you notice any abnormal behavior from your "home assistant," immediately unplug the washing machine. Only then can you begin troubleshooting the equipment. What should you do next? What parts of the washing machine should you pay attention to?

Where did it come from?

What could be the reasons for this error to appear on the display? The instruction interprets the code E21 as the lack of possibility of rotation of the drum. The washing machine is completely blocked and starts the emergency drain.

The E21 error may be triggered by:

• a strong power surge in the electrical network;
• foreign object stuck between the drum and the tank;
• a slipped or broken drive belt;
• failed motor;
• broken tachometer;
• incorrectly functioning electronic module.

When diagnosing any error, start with the easiest problems to check. First, you need to make sure it's not a simple system failure. Rebooting is easy to do yourself. To do this:

• turn off the machine using the button;
• unplug the power cord from the outlet;
• let the washing machine stand for 15-20 minutes;
• Turn the washing machine on again.

If the error disappears and the machine completes the cycle as if nothing had happened, then it's likely a one-time system failure. If the code reappears, you'll need to investigate the cause of the malfunction. The first step is to check the electrical voltage.

The power grid is to blame

Sometimes the E21 error is caused by insufficient voltage in the electrical network. This can be verified with a multimeter. The procedure is as follows:

• unplug the machine's power cord from the socket;
• Use a multimeter to check the voltage at the point;
• Compare the calculated readings with the standard ones (they are specified in the washing machine passport).

If the voltage does fluctuate, you'll need to connect a voltage stabilizer to the power grid. If you don't have electrical experience, it's best to leave this job to a professional.

If fluctuations and surges in your home's electrical system are a frequent occurrence, it's best not to delay installing a voltage stabilizer.

A dangerous object is stuck in the tank.

If you see the E21 error code on your Bosch washing machine's display, be sure to check the drum. Open the loading door and spin the drum by hand. If the spinner moves with difficulty or stops completely, it's likely blocked by small debris, such as a bra underwire, coin, key, etc.

To fix the error, you'll need to remove the foreign object from the washing machine. To do this:

• de-energize the washing machine;
• remove the cover from the case;
• drain the remaining water from the system by unscrewing the debris filter;
• remove the detergent drawer from the machine;
• Unscrew the screws securing the instrument panel;
• disconnect the control panel and place it on the lid of the washing machine without touching the wiring;
• open the loading door;
• Use a slotted screwdriver to pry up the outer clamp securing the drum cuff and pull the ring out;
• insert the sealing cuff into the drum;
• Unscrew the screws holding the front panel of the case, remove the panel and put it aside;
• disconnect the wiring from the heating element;
• press the central heater screw inward;
• gently rocking, remove the heating element from the machine body;
• Remove foreign objects from the tank through the resulting hole.

If your washing machine has a rear-facing heating element, the job will be even easier—you won't have to remove the control panel or front panel. If you're repairing your washing machine for the first time, it's a good idea to take photos of all disassembly steps to avoid mistakes during reassembly.

Element of the drive mechanism

In Bosch washing machines with a commutator motor, the drum rotation is provided by a drive belt. The belt is tensioned around the motor and centrifuge pulley. When the belt slips, the drum spins up and down. If you have a model with an inverter and direct drive, this problem can be ruled out immediately.

Checking whether the drive belt is in place is easy. Remove the back of the washing machine and inspect the drum pulley. Any loose rubber will be lying underneath the machine.

Belts don't just fall off. They either break or stretch. In any case, it's best to buy and tighten a new belt. The parts are inexpensive, and the job is easy to do yourself.

Engine speed sensor

Another possible reason is an incorrectly functioning tachometer sensor. The control unit, receiving incorrect information about the rotation intensity of the electric motor, blocks the cycle, displaying an error on the display. E21. To test the tachogenerator:

• de-energize the washing machine;
• After removing the bolts, dismantle the top and back walls of the machine body;
• find the motor – it is located at the bottom of the washing machine;
• Find a small metal ring on the engine, this is the tachometer sensor;
• disconnect the wires connected to the tachogenerator;
• After setting the multimeter to measure resistance, attach the tester probes to the Hall sensor terminals.

A working tachometer sensor produces a resistance of about 60 ohms.

A broken tachogenerator cannot be repaired. A new Hall sensor is purchased for a specific Bosch washing machine model. Installation is quite simple:

• Use a thin screwdriver to pry up the top cover of the old sensor and remove it;
• remove the fixing bolts;
• remove the failed tachogenerator;
• install a new Hall sensor in its place;
• connect the wiring by connecting the tachometer sensor to the motor;
• Assemble the washing machine body.

Sometimes the error can be resolved by tightening the tachogenerator mountings. Often, poor tightening is the cause of the code display.

Electric motor

If the drum rotates easily by hand, but remains stationary after starting a cycle, the motor is likely the culprit. To check the motor:

• remove the top and back wall of the washing machine;
• tighten the drive belt;
• disconnect the wires connected to the engine;
• Unscrew the fasteners and remove the motor from the washing machine body.

Holding the motor in your hand, check its winding. A multimeter is useful for this. The tester's probes are connected to the motor's fins. The normal resistance deviation is up to 5 ohms.

Additionally, the electric motor housing should be checked for breakdown. Place one multimeter probe on the motor surface, and the other on the winding fins. The device should display the maximum resistance reading, indicating there is no current leakage.

Carbon brushes installed in commutator motors are prone to natural wear. When they wear out, the motor begins to operate incorrectly. The carbon rods must be replaced every 3-4 years.

Replacing the electric brushes is quite simple:

• remove the wire from the brush contact;
• remove the graphite rods from the motor housing;
• clean the engine with an abrasive sponge, then wipe it with a soft cloth;
• Install new electric brushes and connect the wires to them.

Electric brushes are always replaced in pairs, even if only one element is worn out.

After testing the winding and replacing the brushes, reinstall the motor. Then reassemble the machine, plug it in, and run a test cycle. If the drum starts spinning and the error disappears, the repair is complete.

Let's inspect the electronic board

If the control module suddenly fails, the machine's display may display any error, including E21. The board can fail due to sudden power surges, moisture getting inside the washing machine, and other factors. Diagnosing the electronic unit without proper knowledge is impossible. At home, a visual inspection is the only option.

The sequence of actions will be as follows:

• unplug the washing machine;
• remove the cover of the washing machine body;
• remove the powder receptacle;
• detach the instrument panel by unscrewing the screws that secure it;
• Inspect the electronic module carefully.

Stains, rust, swelling, faded coating, and darkened tracks are clear signs that the control module needs repair. It's best to entrust control module diagnostics to a service center. This is complex work that requires specific knowledge and skills.

   

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