A continuously high charge reading should be reported to maintenance. The latter is used only during shop battery charging, and not on the road. Never replace these fuses under load if it can be avoided. In any event the best check is to observe the battery ammeter. 118A on the Engine Cooling System.
Control is entirely automatic.
Manual control is not provided unless the railroad specifies. Then rotate the camshaft manually until each small switch plunger has dropped DOWN as far as it will go. This will keep the shutter magnet valve and fan contactors energized. The standard sander circuit provides for electro-pneumatic operation with sanders ahead of each truck in either direction. It is piped into the engine crankcase which is normally at a pressure of less than atmospheric.