Heater shows E07 and refuses to start; fan may not run.

Safety first: Turn off power and allow the heater to cool completely before touching any internal components.

• Check water flow: Confirm that the pump is running and that filter pressure is normal. Clean or backwash the Kripsol filter and ensure all valves are open.
• Reset high limit: Locate the Kripsol high limit thermostat on the heat exchanger header. Press the red or recessed reset button if present. If it immediately trips again, do not continue resetting; find the cause of overheating.
• Inspect for scale: If the heater is used with hard water and not regularly treated, internal scale can cause localized overheating. Look for signs of boiling or popping noises when running. Descaling should be performed by a professional.
• Test high limit switch: With power off, disconnect the switch and test continuity at room temperature. Replace the Kripsol high limit thermostat if it remains open when cool.
• Re-test system: After restoring flow and resetting/replacing the switch, power up the heater. Persistent E07 indicates a deeper flow or exchanger issue requiring service.