You might reset the toothbrush. If it is it on the EasyStart feature, you will have to de-activate it.

• If your toothbrush is on EasyStart mode, you will hear 2 beeps immediately after turning on your Sonicare (it is easier to hear the beeps if the brush head is attached). 
• To deactivate Easy-start feature, attach your brush head to the handle and place the handle in the charger.  Make sure the charger plugged in. Then press and hold the power button for 5 seconds. You will hear 1 beep to indicate that the Easystart feature has been deactivated. 
• If vibration is still weak contact customer service.