E13 or a filter icon with an exclamation mark appears shortly after starting, even with seemingly clean filters.

Safety first: Remove the battery before accessing internal components.

• Step 1 – Verify correct filters: Ensure you are using the correct Princess pre‑motor and HEPA filters specified for your model. Non‑original filters may not seat properly and can trigger errors.
• Step 2 – Inspect filter seals: Check rubber gaskets around the filters for damage or misalignment. Reseat filters firmly so no air can bypass them.
• Step 3 – Clean sensor ports: Locate any small holes or tubes near the filter housing that lead to the pressure sensor. Use a soft brush or compressed air (gentle bursts) to clear dust.
• Step 4 – Reset the unit: Reinstall the battery and hold the mode or power button (depending on model) for 5–10 seconds to reset filter indicators, if the manual describes such a function.
• Step 5 – Replace sensor/PCB: If E13 persists with correct, clean filters and clear ports, the pressure sensor or its circuit on the control PCB is likely defective. Replace the main control PCB or sensor module via an authorized service center.