my dyson v8 won't turn on, just makes a pulsing noise. what's going on?

It's blocked. The machine has an automatic cut-out that pulses the motor and stops function when there's a blockage.

FIX: First, disconnect from the charger. Let the machine cool down. Do not touch the trigger. Then, check these points in order:

1. Open the bin. Check in and around the cyclones and the tool/wand attachment point.
2. Remove the wand from the machine. Remove the cleaner head from the wand. Check for blockages at both ends of the wand.
3. Turn the cleaner head over. Check the brush bar and air inlet for obstructions.

Remove any debris you find.

IF THAT DIDN'T WORK: The battery is empty. The machine shows a flashing blue, green, or red light on the mode button when the battery is low. Connect it to the charger for a full charge, which takes about 4 hours. The LED will flash while charging and turn off when fully charged.

HEADS UP: The machine won't operate or charge if the ambient temperature is below 5°C (41°F). This protects the motor and battery.