Display shows E10; heater function disabled and water remains cold on heated Kärcher carpet cleaner models.

Safety first: Unplug the unit and allow it to cool completely before working on the heater assembly.

• Check for scale buildup: Inspect the heater block and water path for limescale. Heavy scale can cause overheating and trip safety devices.
• Test heating element: Access the heater terminals and measure resistance with a multimeter. An infinite reading indicates a failed heating element that must be replaced.
• Inspect thermal fuse/thermostat: Many Kärcher heaters include a thermal fuse or resettable thermostat. Check continuity; if open and non-resettable, replace the fuse assembly.
• Check NTC sensor: Measure the resistance of the NTC temperature sensor at room temperature and compare with service data. Replace if out of range or open.
• Control PCB relay: If the heater and sensors test OK, inspect the heater relay on the main PCB for burn marks or pitted contacts. Replace the PCB if the relay has failed.