Heater shows E05 and will not start; water is circulating but no heating occurs.

Safety first: Disconnect power before accessing the control compartment or sensor wiring. Do not bypass temperature sensors; this can cause overheating.

• Locate the inlet sensor: Find the Kripsol NTC sensor threaded into the heater’s inlet manifold or attached via a sensor well.
• Inspect wiring: Check the cable from the sensor to the control board for cuts, abrasion, or rodent damage. Reseat the connector at both ends.
• Test sensor resistance: With the sensor disconnected and the water at a known temperature (e.g., 25°C), measure resistance with a multimeter. Compare to Kripsol’s NTC chart. If the reading is open, shorted, or far off spec, replace the sensor.
• Check for moisture: Inspect the sensor pocket and connector for signs of water ingress or corrosion. Dry thoroughly and correct any leaks in the manifold.
• Replace if needed: Install a new Kripsol inlet NTC sensor using thread sealant approved for potable water. Reconnect wiring, restore power, and clear the error.