Error Code: F21 Difficulty: Hard
Problem: Motor-related fault, often due to a malfunctioning tachogenerator.
How to Fix F21 Error (Step-by-Step)
- Unplug the dryer from the wall outlet to ensure your safety.
- Remove the top panel of the dryer, usually held by screws at the back.
- Take off the control panel and front panels to access the dryer’s internal components. Keep all screws organized.
- Carefully lift and remove the dryer drum to expose the motor assembly at the bottom rear of the machine.
- Locate the tachogenerator (a small component with wires) on the end of the motor. Disconnect its wiring harness and remove the screws holding it in place.
- Install the new tachogenerator, ensuring it is securely screwed in and the wiring harness is reconnected properly.
- Reassemble the dryer by reinstalling the drum, front panels, control panel, and top panel in the reverse order you removed them.
- Plug the dryer back in and run a test cycle to confirm the F21 error is cleared.
Still Not Working?
If the replacement part didn’t fix the issue, you may have a wiring problem or main board failure.
What to Check Next on This Bosch Dryer
Use these checks before ordering parts for Bosch dryer F21. They keep the diagnosis tied to the appliance instead of turning the page into a reset-only guide.
- Unplug the dryer before touching the lint housing, rear vent, lower service area, or any wiring.
- Clean the lint screen, moisture sensor bars, condenser area if equipped, and the full vent path so airflow problems do not imitate part failures.
- Run a short timed cycle with a light load and note whether the fault appears immediately, after heating starts, or near the end of the cycle.
- If the fault returns with clean airflow, inspect the part categories below using the full model number from the dryer tag.
- Stop repeated test cycles if you smell heat, see moisture near electrical areas, or hear grinding from the drum drive.
Recommended Parts to Check
Bosch dryer part numbers vary by model. These are model-number-safe part-category searches, not universal fit claims.
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Dryer lint screenCommon replacement category: lint filterFit note: Exact OEM part number varies by full model number. Confirm compatibility before buying.Why check it: Start with lint restrictions when heating, airflow, or maintenance warnings appear.
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Dryer thermal fuseCommon replacement category: thermal protectionFit note: Exact OEM part number varies by full model number. Confirm compatibility before buying.Why check it: Common safety device to inspect after overheating or no-heat symptoms.
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Dryer drum beltCommon replacement category: drive systemFit note: Exact OEM part number varies by full model number. Confirm compatibility before buying.Why check it: Worth checking when the dryer tumbles poorly, stalls, or makes drive noise.
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Dryer moisture sensorCommon replacement category: sensor circuitFit note: Exact OEM part number varies by full model number. Confirm compatibility before buying.Why check it: Useful category to verify when dryness or care/maintenance messages persist.
Before ordering: match the part to the complete model number on the appliance tag.
More options (for a better recommendation)
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Expert: Mike Sullivan
EPA Section 608 Certified Technician with 18+ years experience.
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When It’s Better to Replace Than Repair
Dryer repairs are often worth it for small parts, but repeated heating, motor, drum, or control failures can point toward replacement.
Confirm gas vs electric, venting, voltage, doorway clearance, and laundry-space dimensions before ordering.
For repair parts, verify exact fit with the full dryer model number before buying; these links are general replacement-appliance shopping options.
- [OK]Thermal fuse or heater failures keep returning
- [OK]Belt, roller, or motor repairs exceed unit value
- [OK]Door switch or control issues stack with other faults
- [OK]Older dryer has long dry times even after vent cleaning
Recommended Dryer Replacement Options
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