ALTERNATOR AND WIRING GROUP 3Y4449 - Caterpillar

Generators Used With 3412, 3508, 3512, 3516, D379, D398, D399 EnginesUse care when printed circuit boards are installed in the M5 Power Supply And Interconnection (Host) Board on the above generators. The M5 Host Board is one of the boards used in the A-5 Cage Assembly (metal). Two of the additional circuit boards used in the A-5 Cage Assembly, are fastened to the 5N9090 Bracket (part of the A-5 Cage Assembly) with screws. When a new M3 Trip/Alarm Switch Board or M4 Excitation Output Board is installed in the M5 Host Board, the screw holes in the boards may not align with the screw holes in the 5N9090 Bracket.
Alignment of the holes between the circuit boards and the 5N9090 Bracket, should be done by bending the bracket (metal) or drilling new holes in the circuit boards.
If the circuit boards are forced into alignment with the bracket, the M5 Host Board can be damaged, see Illustration 1. Damage to the slots in the M5 Host Board, can let the M3 and M4 Circuit Boards move out of correct alignment. Several different failure modes can result. If a generator set experiences several repeat failures, check for connector damage in the M5 Host Board.
If new alignment holes are drilled, be careful not to drill through a circuit track on the board.
Illustration 1. Circuit Board Connectors.
Illustration 2. A-5 Cage Assembly.