Burner starts briefly then shuts down; display shows E02 and no sustained hot water.

Safety: Switch off power and close the gas shut-off valve before opening the combustion chamber.

• Check combustion air and flue: Ensure the Weishaupt concentric flue terminal is not blocked by leaves, snow, or debris. Restricted air or flue gas paths can cause flame instability.
• Inspect burner and injector: Remove the burner assembly as per the service manual. Check the premix burner surface and gas injector for dust, rust flakes, or scale. Clean with a soft brush and compressed air (do not damage the burner mesh).
• Clean flame sensor: Gently clean the flame sensor rod with fine abrasive pad to improve signal quality.
• Check gas supply stability: Reopen the gas valve and observe if other gas appliances cause pressure drops when they start. If so, a gas supply issue may exist and must be addressed by a licensed gas fitter.
• Professional check: If E02 persists, a Weishaupt technician should measure ionization current, verify gas valve modulation, and check the control board.