ARMY TM 9-6115-670-14&P 4-136 4.53.  MAIN AC CONTACTOR. This task covers:  a. Test b. Replace INITIAL SETUP Tools General Mechanic's Tool Kit (Item 1, Appendix B) Shop Equipment, Electrical Repair, Semitrailer Mounted (Item 3, Appendix B) Equipment Conditions MASTER ON-OFF switch on APU control unit set to OFF. Contactor mounting plate removed (para 4.52.). Materials/Parts Main AC Contactor Reference: Figure FO-1 TEST a.  Refer to Figure FO-1 (SICPS/WIN-T) or F0-7 (JTACS) and tag and disconnect electrical leads from terminals T1, T2, and T3 on main AC contactor by loosening three screws. b.  Using a Multimeter, test for continuity between terminals L1 and T1 on main AC contactor. There should be no continuity. c.  Refer to Figure 4-41, sheet 1, and apply 24 VDC across main AC contactor (1) terminals A1 and A2 by connecting positive lead from a power supply to terminal A1 and negative lead from power supply (5) to terminal A2. d.  Repeat step b. There should be continuity. e.  Remove 24 VDC. Continuity between L1 and T1 should be broken. f.   Perform steps b through e, testing continuity between L2 and T2 and L3 and T3 on main AC contactor (1). g.  If any pair of contacts fails the continuity test, the main AC contactor is defective. Replace main AC contactor. WARNING Ensure that APU DC power supply is disconnected. Failure  to  observe  this  warning  could  result  in severe injury or DEATH to personnel. WARNING Ensure that the APU is turned off and completely de-energized before opening generator housing. Failure  to  observe  this  warning  could  result  in severe injury or DEATH to personnel.