F24 Miele

F24 = heater relay contact fault (Miele dishwasher).

The board runs a self-check on the heater relay — early in the cycle it sends a signal and expects to see it back. If the computer doesn’t get a signal back from the relay, it stops the cycle and faults. Often trips almost immediately after start.

Most common causes, in order:

• Welded/stuck relay contacts on the main PCB — the usual culprit. The relay is more likely to fail closed (contacts sticky from arcing).
• Corroded relay contacts — usually from a voltage spike, or over-sudsing that leaks into the base pan and corrodes the contacts.
• Heater element in the circulation pump, or wiring in the heat circuit — less common.

On-site check: the heater relay is a simple mechanical switch — the top comes off for inspection. Access it by removing the base pan (4x T20), machine on its side. Contacts can be cleaned up with a points/nail file to confirm diagnosis, but heads-up — cleaning contacts sometimes clears the F24 but leaves the timer stuck, and replacing the relay doesn’t always resolve it if the fault’s actually on the board.