Cordless vacuum runs but suction is very weak; an E3 indicator or three flashing LEDs appear when switching to high power.

Safety first: Turn OFF the vacuum and remove the battery before disassembling the dust cup or filters.

Steps to try:

• Empty and clean dust cup: Remove the dust cup from the Eureka cordless unit. Empty debris and wipe the interior with a dry cloth. Check the rubber gasket at the top and bottom of the cup for cracks or deformation.
• Clean pre-motor filter: Remove the foam and felt filters (often located above the dust cup). Tap them gently over a trash can to remove dust. If washable, rinse under lukewarm water until clear, then air-dry for at least 24 hours before reinstalling.
• Inspect cyclone vents: Fine dust can clog the cyclone shroud. Use a soft brush to clean the perforated metal or plastic screen. Avoid sharp tools that could puncture the mesh.
• Check for leaks: Reassemble the dust cup and ensure it locks firmly into place. If the cup feels loose or you hear air hissing around the seal, the dust cup or seal may be damaged.
• Test suction at main body: Remove the wand and nozzle, then test suction directly at the main body inlet. If suction is strong here but weak at the floor head, the wand or nozzle is partially blocked.
• Replace worn seals: If you see flattened or torn rubber seals around the dust cup or cyclone, replace the dust cup assembly or gasket to restore full suction.