What to check, in order
- Reset at the breaker
Bosch US suggests switching the power off at the circuit breaker for 30 seconds, then back on.
- Salt light on too?
Bosch UK says to check the salt sensor isn't dirty if the salt light is also showing.
When to call an engineer
If it keeps happening, book an engineer. The heater runs on mains power inside a wet appliance, so it isn't a DIY job.
A repair visit will usually check the heating element, its temperature sensor and the wiring back to the control board.
Before you book
- Note the model and serial number. They're on a label on the edge of the door or the side of the tub.
- Write down the exact code, and what the appliance was doing when it appeared.
- Check whether it's still under warranty. If it is, the repair may cost you nothing.
Checked against
Last reviewed September 2026. Manufacturers update their pages, and your manual is the final word.