Install two diodes (13) using two screws (14), six lockwashers (16), and two nuts (15).
Install relay (10) using eight screws (11) and eight lockwashers (12).
Install gasket (7) and relay switch cover (6) using 16 lockwashers (9) and 16 screws (8).
No calibration is required if APU or switching relay box is removed and reinstalled with no change
System must not be operated four hours prior to performing this calibration procedure.
Place multimeter on one volt scale, and connect black lead (39) to wire of circuit 478A (40) at switching relay box (3) (i.e.,
sharpen tip with file, and puncture circuit 478A insulation).
Connect red lead (41) of multimeter onto a piece of extension wire, and connect other end of wire to mounting screw (42)
of APU flywheel guard (43) inside APU access door (44).