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In TT of your vintage , there will probably be a metal panel 6"x 12" brown in color; could have vent louvers ; that hinges down or has to be slid up to remove , to expose the 120 volt breakers and 12 volt fuses .
Sorry I don't have a photo with the cover closed .
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.