F04Serious
Bosch Dryer F04 Error Code
The heater relay on the control board is stuck open or closed, causing no heat or continuous heat.
Common causes
- Defective relay on control board
- Control board failure
- Moisture damage to electronics
How to fix it
- Unplug dryer and check for visible burn marks on control board.
- Test relay with multimeter (if skilled) or inspect for swollen capacitors.
- Reset by unplugging for 30 minutes.
⚠ When to call a pro: If relay is faulty, replace the control board; for safety, call a technician.
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Always unplug the appliance (and turn off the water for washers/dishwashers) before inspecting. These guides are for information only and are not a substitute for a professional repair.