xld int light + electronic mystery's help

1996 XLD ELECTRICS hi all can anyone tell me why i have no light when i open any door, the roof light switch has to be moved from the open doors to the light on position and that works ok,

and can someone say if this car should have an alarm or imobialiser or not, ive looked every where the fuses are all ok i can't find any switch as the hanes book says, so how does one get to the answers of these questions,

thanks for your time brian