Runs down and stops in about a second
My toothbrush runs down and stops in about a second. I fixed the problem a few months ago by unsoldering and then resoldering the battery. I have checked the battery voltage during the switch on, slow down and stop phase and it remains constant at about 3.7V so there would seem not to be a problem with the battery. When the problem occurred before I found that bypassing the MOSFET caused the motor to run normally at full speed, so this seems to be a microprocessor issue. I have tried resetting the brush by holding the power button for ten seconds. There is no water inside.