Bosch · Dryer
Bosch Dryer E12 Error Code
Heat pump overheating from limescale or blocked airflow
What this error means
E12 on Bosch heat-pump dryers signals overheating—official guidance cites limescale buildup in the heat pump when airflow was already restricted. The dryer shuts down to protect the sealed refrigeration circuit and heating components.
How E12 is detected
When E12 appears on a Bosch dryer, the control board has confirmed that water did not leave the machine within the programmed drain window. On Bosch WQB245AXUC, Bosch WTG865H4UC, and similar variants, the drain pump runs for a fixed interval—often three to seven minutes on washers and dishwashers—while a pressure switch or turbidity sensor verifies the tub or sump is empty. If water remains, the cycle stops to prevent spin with a full tub or overflow on the next fill.
Most E12 calls are resolved without parts: allow the dryer to cool completely—thirty minutes minimum—before any work. Restricted drain paths mimic pump failure because the impeller spins against a blocked hose or filter. Document whether the pump hums audibly during the drain step; a humming pump with no water movement points to a clogged filter or kinked hose, while silence may indicate a failed pump motor or loose wiring at the harness.
After clearing blockages, run a short cycle and listen at the drain hose for steady water flow. If E12 returns on the next load with a clean filter and straight hose, measure resistance at the pump motor connector per the service manual for your model before ordering a replacement pump assembly.
Common causes
- Limescale coating the heat exchanger in hard-water regions
- Lint-blocked condenser after skipping maintenance cycles
- Crushed vent transition on vented hybrid installs
- Thermal limiter tripped from a prior long cycle on a packed drum
Step-by-step fixes
- 1Allow the dryer to cool completely—thirty minutes minimum—before any work
- 2Clean the lint filter and rinse the removable condenser under running water
- 3Run Bosch's basic appliance care program if your model displays CrE reminders
- 4Descale per manual if you are in a hard-water area and E12 followed months of heavy use
When to call a technician
E12 returning immediately after condenser cleaning and care program may require heat-pump service or thermal limiter replacement.
Affected models
- Bosch WQB245AXUC
- Bosch WTG865H4UC
- Bosch WTG86401UC
Prevention & maintenance
- Clean drain filters and hose terminations monthly on high-use dryers to prevent E12 from lint and food debris buildup.
- Record when E12 appears in the cycle and whether it clears after a 60-second power reset on your Bosch dryer—that detail speeds diagnosis if you call service.
- Keep the model and serial number from the rating plate when ordering parts for E12; Bosch uses multiple revisions with different harness lengths and board firmware.
- Photograph wiring connector orientation before disconnecting any component while troubleshooting E12; reversed plugs on pumps and valves cause immediate repeat faults.