Truck Repair: 1990 brake fuse location, engine brakes, brake switch

Question
can you tell me where the fuse for the brake lights is hidden on a 1990 cummins? or maybe tell me where I could find  a online repair manual?

Answer
Engine Brake??Engine brakes are operated by switches in the dash & controled by the ECM.If they do not work,there is probably a bad switch like Clutch switch,on/off,brake switch or selector.A sure thing if cruise does not work too.Or just a bad relay if cruise works.