Alternating red and blue lights on a Dyson V8 identify a charger fault, unlike a flashing blue empty-battery signal. First separate an airflow, fitting or temperature-protection problem from an electrical fault. Do not open the motor body: the checks below stay within the user-maintenance steps described by the manufacturer. What the alert means: Dyson assigns the red-and-blue alternating pattern to the charger, while a red-only warning points elsewhere in the machine. What to distinguish first: Observe the pattern while connected to a known working wall socket and check the lead and plug for visible damage. 1. Confirm the exact symptom — Dyson assigns the red-and-blue alternating pattern to the charger, while a red-only warning points elsewhere in the machine. 2. Prepare safely — Switch off, unplug the charger or mains lead and let the machine cool before removing user-accessible parts. 3. Apply the official check — Reconnect the charger directly to the wall, ensure the charging plug is fully seated and compare the light sequence with Dyson's key. 4. Interpret one retest — If red and blue continue to alternate on a sound outlet, do not try another random charger; use Dyson support for the correct unit. The official Dyson procedure identifies this exact symptom and supports the checks above. Do not probe the battery, charger, motor or internal wiring and never refit a damp filter. Stop using the vacuum for a burning smell, unusual heat, damaged cable or a warning that returns after the official check.
Models covered
Safety first
- Do not probe the battery, charger, motor or internal wiring and never refit a damp filter.
What the symptom may indicate
Checks in the right order
- Confirm the exact symptom
Dyson assigns the red-and-blue alternating pattern to the charger, while a red-only warning points elsewhere in the machine.
- Prepare safely
Switch off, unplug the charger or mains lead and let the machine cool before removing user-accessible parts.
- Apply the official check
Reconnect the charger directly to the wall, ensure the charging plug is fully seated and compare the light sequence with Dyson's key.
- Interpret one retest
If red and blue continue to alternate on a sound outlet, do not try another random charger; use Dyson support for the correct unit.
Stop and get qualified help when
- Stop using the vacuum for a burning smell, unusual heat, damaged cable or a warning that returns after the official check.
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
- Dyson — The official Dyson procedure identifies this exact symptom and supports the checks above.
Last checked: 30 August 2026