Washer-dryer combo shows D18 and may not fill or drain correctly, sometimes accompanied by unusual water level behavior.

Safety first: Unplug the appliance and shut off water supply if there is any sign of overflow.

• Verify drain hose installation: Ensure the drain hose is not inserted too far into the standpipe and that it has an anti-siphon loop at the correct height per Brandt instructions.
• Clean pressure system: Access the pressure switch and its hose. Remove the hose and blow through it to clear blockages. Clean the air chamber on the tub if accessible.
• Test pressure switch: Use a multimeter to verify switching at different pressure levels. Replace the pressure switch if it does not operate correctly.
• Control board reset: After cleaning and replacing parts, unplug the machine for several minutes to reset. If D18 persists, the control board may require replacement.