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Er:21

Bosch · WAT28400UC 2.8 cu ft Compact Front Load Washer

Bosch WAT28400UC 2.8 cu ft Compact Front Load Washer Er:21 Error Fix: Motor Tachometer Error

The motor tachometer (speed sensor) is not sending a signal to the control board. The tachometer monitors motor RPM for precise speed control during wash and spin cycles. Check the tachometer sensor (hall sensor) on the motor for damage. Verify the wiring harness between the motor and motor control board. If the sensor is integrated into the motor, the motor stator may need replacement.

High severity2 fixes available✨ Free fix available

Quick Answer

Error Er:21 on the Bosch WAT28400UC 2.8 cu ft Compact Front Load Washer means: Motor Tachometer Error. The top-ranked community fix is “Replace Motor with Integrated Tachometer Sensor” (hard difficulty, ~90 min, DIY cost: $0). 2 community-ranked fixes available below.

Published February 2026 · 2 fixes · washer

Content is based on manufacturer service documentation, community repair experience, and OEM technical bulletins. Always verify with your owner's manual.Learn about our editorial standards.

When to Call a Professional

While many washer repairs can be done safely at home, consider hiring a qualified technician if:

This is a high severity error — continued use may cause damage or a safety hazard
The repair involves electrical wiring, gas lines, or refrigerant
You've tried the top-ranked fix and the error persists
You smell gas, see sparking, or notice water leaking
The repair requires specialized tools you don't have
Your appliance is still under manufacturer warranty

Average professional repair cost for this issue: $300-$450.

Other Bosch Models with Error Er:21

WAT28401UC 2.2 cu ft 300 Series Compact Washer

washer · 2 fixes

WAW285H1UC 2.2 cu ft 800 Series Compact Washer

washer · 2 fixes

WAW285H2UC 2.7 cu ft Compact Front Load Washer with EcoSilence Motor

washer · 2 fixes

Other Bosch WAT28400UC 2.8 cu ft Compact Front Load Washer Error Codes

Door Lock Fault

Water Not Draining

Water Fill Timeout

Heating System Fault

Overfill — Water Level Too High

Motor / Drive Fault

No Spin — Imbalance Detected

2 fixes

Er:13

Inlet Valve / Aquastop Fault

2 fixes

People Also Ask About Bosch WAT28400UC 2.8 cu ft Compact Front Load Washer Error Er:21

What does error code Er:21 mean on a Bosch WAT28400UC 2.8 cu ft Compact Front Load Washer?

Error code Er:21 on the Bosch WAT28400UC 2.8 cu ft Compact Front Load Washer means: Motor Tachometer Error. The motor tachometer (speed sensor) is not sending a signal to the control board. The tachometer monitors motor RPM for precise speed control during wash and spin cycles. Check the tachometer sensor (hall sensor) on the motor for damage. Verify the wiring harness between the motor and motor control board. If the sensor is integrated into the motor, the motor stator may need replacement.

How do I fix error code Er:21 on my Bosch WAT28400UC 2.8 cu ft Compact Front Load Washer?

The most successful fix is "Replace Motor with Integrated Tachometer Sensor" (hard difficulty, ~90 minutes). This fix costs nothing. HomeMD has 2 community-ranked fixes for this error.

Is error code Er:21 on a Bosch WAT28400UC 2.8 cu ft Compact Front Load Washer serious?

This error is rated high severity. You should address it promptly — continued use could cause damage or safety concerns.

Can I fix Bosch WAT28400UC 2.8 cu ft Compact Front Load Washer error Er:21 myself?

Yes — the top-ranked community fix ("Replace Motor with Integrated Tachometer Sensor") is rated hard difficulty and takes about 90 minutes. Tools needed: T20 Torx screwdriver, 10mm socket wrench, Multimeter.

How much does it cost to repair Bosch WAT28400UC 2.8 cu ft Compact Front Load Washer error Er:21?

DIY cost: $0. Professional repair typically costs $300-$450. Many homeowners save money by trying the top-ranked community fix first.

What other error codes does the Bosch WAT28400UC 2.8 cu ft Compact Front Load Washer have?

The Bosch WAT28400UC 2.8 cu ft Compact Front Load Washer has 8 other known error codes, including: Er:01 (Door Lock Fault), Er:02 (Water Not Draining), Er:05 (Water Fill Timeout), Er:07 (Heating System Fault), Er:08 (Overfill — Water Level Too High), and 3 more.

Which other Bosch models have the Er:21 error?

Error code Er:21 also appears on 3 other Bosch models: WAT28401UC 2.2 cu ft 300 Series Compact Washer, WAW285H1UC 2.2 cu ft 800 Series Compact Washer, WAW285H2UC 2.7 cu ft Compact Front Load Washer with EcoSilence Motor. The fix may vary by model, so check each model's specific page for tailored repair steps.

What other error codes does the Bosch WAT28400UC 2.8 cu ft Compact Front Load Washer have?

The Bosch WAT28400UC 2.8 cu ft Compact Front Load Washer has 8 other known error codes:

Er:01 — Door Lock Fault (2 fixes)
Er:02 — Water Not Draining (2 fixes)
Er:05 — Water Fill Timeout (2 fixes)
Er:07 — Heating System Fault (2 fixes)
Er:08 — Overfill — Water Level Too High (2 fixes)
Er:10 — Motor / Drive Fault (2 fixes)
Er:11 — No Spin — Imbalance Detected (2 fixes)
Er:13 — Inlet Valve / Aquastop Fault (2 fixes)

Which other Bosch models have the Er:21 error?

Error code Er:21 also appears on 3 other Bosch models:

WAT28401UC 2.2 cu ft 300 Series Compact Washer (washer) · 2 fixes
WAW285H1UC 2.2 cu ft 800 Series Compact Washer (washer) · 2 fixes
WAW285H2UC 2.7 cu ft Compact Front Load Washer with EcoSilence Motor (washer) · 2 fixes

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