A few things you should know when repairing a charger:
Most chargers can hold a charge long after they have been unplugged or disconnected from the battery. You can be shocked by an unplugged charger. The consumer assumes all risk when repairing or utilizing a charger that has been "repaired" or modified. In addition, once the charger has been opened all warranties are null and void. In addition, and state of federal inspections and approvals (such as UL, CE) are terminated.