The boost solenoid and 12v house solenoid are large amperage devices and can cause a lot of problems when they go wrong. Also the charging system uses a diode isolator to allow the alternator to charge the house and chassis batteries at the same time while maintaining electrical separation. This isolator is also a cause for problems when it fails. Projects were done to redesign both of these systems for lower current draw when on (for the house solenoid) and to remove the need for an isolator diode system. This is broken out to make it easier for people to find the information.