Thermostat displays E15 and indicates a schedule or clock synchronization error; timed programs may not run correctly.

Safety: No electrical work is needed.

• Check Wi‑Fi and cloud: Resolve any connectivity errors (E01/E02) so the thermostat can sync time from Bosch servers.
• Set time manually: In the thermostat menu or Bosch app, manually set the correct time, date, and time zone.
• Update firmware: Ensure the thermostat is running the latest firmware, which may fix clock or scheduling issues.
• Factory reset if needed: If schedules behave erratically, back up your settings, perform a factory reset, and re‑enter schedules.
• Replace if clock drifts severely: Persistent large time drift after fixes suggests an internal clock circuit fault; replace the thermostat.