Display shows E15; unit may shut down when multiple elements should be active.

Safety: Turn OFF power at the breaker before testing elements or wiring.

• Check stage wiring: For multi-element EcoSmart models, verify that each element stage harness is connected to the correct terminals on the control board and heating modules.
• Test each element: Disconnect and measure resistance of each element. An open circuit indicates a failed element that must be replaced.
• Inspect connectors: Reseat the multi-pin connectors between the control board and element banks.
• Test operation: After replacing any bad elements and securing connections, restore power and run hot water at high demand to see if E15 recurs.
• Board replacement: If all elements are good but one stage never energizes and E15 persists, the stage driver on the control board may be defective and require replacement.