E9 is displayed and the unit may stop with water dripping or internal beeping.

Safety first: Turn off power before working near water and electrical components.

Steps:

• Check drain hose: Locate the condensate drain hose from the indoor unit. Ensure it slopes downward continuously and is not kinked or elevated.
• Clear blockage: Use a wet/dry vacuum at the end of the drain hose outside to suck out sludge and algae. Alternatively, blow compressed air gently from the indoor side if accessible.
• Clean drain pan: Remove the front cover and inspect the drain pan for slime or debris. Clean with mild detergent and water, taking care not to spill into electrical areas.

For units with drain pump: If the pump does not run when the pan is full, the pump or float switch may be defective. Replacement of the Bosch drain pump kit should be done by a technician.