Cordless vacuum will not start and shows E04 immediately when powered on

Safety first: Remove the battery and keep metal objects away from the battery terminals.

• 1. Verify battery compatibility: Ensure you are using a Festool-compatible cordless vacuum battery (correct voltage and system series). Refer to the Festool manual for approved battery models.
• 2. Clean battery contacts: Inspect the battery terminals and the vacuum's battery interface contacts. Use a dry, lint-free cloth and a soft brush to remove dust. Do not use solvents or sprays.
• 3. Check for bent pins: Look closely at the small data/communication pins in the battery interface. If any are bent or recessed, do not force the battery in. Bent pins require replacement of the battery interface board.
• 4. Test with another Festool battery: If available, insert a known-good Festool battery that works in other tools. If E04 clears, the original battery pack is likely faulty and should be serviced or replaced.
• 5. Inspect battery interface board: If multiple good batteries all trigger E04, the internal battery interface PCB or wiring may be defective. This repair involves disassembling the housing and should be performed by an authorized Festool technician.