Most voltage regulators are damaged because of the breakdown of internal field effect transistors or Darlington transistors, which makes the excitation current out of control, the output voltage of the generator will rise and the battery will be overcharged. Damage to the generator will reduce the output voltage and cannot charge the battery. Most of the above faults exist, but there are exceptions, such as open circuit damage of effect tube or Darlington tube, grounding of generator excitation winding lead, etc.