On the Kärcher FC7, a fill-water warning with a visibly full fresh-water tank does not automatically mean that the tank or pump has failed. The official manual identifies two user-checkable causes: the sensor in the tank holder can be dirty, and distilled water may not be detected correctly. Switch the cleaner off and remove the fresh-water tank. Inspect the tank for cracks or leakage, then clean only the visible holder sensor gently with a clean cotton swab; do not pour liquid into the holder or probe the wiring. Fill with ordinary tap water and the approved detergent dose, avoiding distilled water, and seat the tank completely. Restart once and allow a short moment for the indication to update. If the warning remains, the sensor circuit needs qualified service. This guide deliberately does not link an unverified tank or sensor because the catalog does not prove an exact FC7 replacement for this symptom.
Models covered
Safety first
- Keep the tank holder and electrical contacts dry; do not scrape the sensor, bridge contacts or dismantle the cleaner.
What the symptom may indicate
Checks in the right order
- Power off and remove tank
Switch off, disconnect the charger or plug, lift out the fresh-water tank and place it on a dry surface.
- Clean the visible sensor
Use a clean dry cotton swab on the sensor in the holder without pressing hard or introducing fluid.
- Use tap water
Empty distilled water if present, fill to the mark with tap water and only the approved cleaner quantity.
- Seat and restart once
Push the tank fully home, power on and wait briefly; repeated cycling will not repair a faulty sensor.
Stop and get qualified help when
- Stop if the tank leaks, contacts are wet or corroded, the warning remains after the documented checks, or the cleaner behaves unpredictably.
Next step
Repair, replace a part, or arrange a diagnosis?
Use the checks and stop conditions above to choose a cautious next step. A symptom alone never proves that the appliance has failed.
Resolve it without buying anything
Complete the 4 user-accessible checks in order. If normal operation returns and no warning sign remains, no replacement is indicated.
Replace only the confirmed part
If the checks isolate a worn or blocked component, match its complete reference to the exact appliance model before ordering.
This guide does not identify a replacement part. Do not order a generic component from the symptom alone.
Arrange a diagnosis before replacing the appliance
Stop at any warning sign listed above. A qualified diagnosis should confirm that repair is unsafe, unavailable or uneconomical before an appliance replacement is considered.
Sources used
- Kärcher — The official FC7 manual states that a full-tank warning can result from a dirty holder sensor or distilled water and instructs cleaning the sensor with a cotton swab.
Last checked: 30 August 2026