M35a3 CTIS diagnosis

[HFDm715]

Recieved an M35a3 from Forest Fire service for our Fire dept, the CTIS does not power up, I do not have a book on the system, can someone tell me where it gets its feed from? is it fused? I am a Tech so I know how to use a Fluke meter and read I wiring diagram, just havent found one yet for it, also wondering if there is a Central area where Fuses,relays etc are?

any help would be appreciated

Duane