Heater displays E07 and will not heat; may occur intermittently as water warms

Safety: Turn off power and allow the heater to cool before touching plumbing or sensors.

• Locate outlet sensor: Identify the Outlet Water Temperature Sensor on the outlet header or manifold.
• Inspect and reseat connector: Disconnect the sensor plug at the control board and at the sensor (if applicable). Check for bent pins or corrosion. Reseat firmly.
• Measure sensor resistance: With the sensor disconnected, measure resistance and compare to the SunHeater chart. Replace the sensor if readings are out of range.
• Check for overheating causes: If the outlet header feels extremely hot compared to the inlet, verify water flow (clean filter, open valves). Poor flow can overheat the outlet sensor and trigger E07.
• Test operation: After replacing or reconnecting the sensor, restore power and run the heater while monitoring outlet temperature. If E07 recurs with normal temperatures, suspect a control board fault.