Dishwasher shows E12; heavy limescale deposits may be visible in the tub or on heating components.

Safety first: Disconnect power and allow the machine to cool before descaling.

E12 indicates that limescale build-up is affecting heating or water flow.

• Step 1 – Check salt and softener settings:
  • Ensure the salt reservoir is filled with dishwasher salt (not table salt).
  • Verify the water hardness setting in the dishwasher menu matches your local water hardness.
• Step 2 – Run a descaling cycle:
  • Purchase a Siemens-approved dishwasher descaler.
  • Follow the product instructions: usually run an empty hot program with the descaler placed in the machine.
• Step 3 – Inspect heat exchanger:
  • Remove the left side panel and visually inspect the heat exchanger/water matrix for heavy white deposits.
  • If heavily scaled, multiple descaling cycles may be required.
• Step 4 – Manual cleaning (advanced):
  • In severe cases, the heat exchanger or heater/heat pump assembly may need to be removed and replaced.

To prevent recurrence, always keep salt filled and use rinse aid; consider installing a whole-house softener in very hard water areas.