I don't understand "connect the battery cables (with a fuse of 7 amps between)". Is there an in-line 7 amp fuse between the battery and main power going to the underdash harness? If so, typically more than 7 amps is used when the key is in ACC or RUN.
If you are talking about the 7.5 amp fuse in the fuse box, that controls the courtesy lights: doorjamb, underdash courtesy lights, glove box, accessory lights not part of the dash lamp fuse system, etc. This typically blows due to shorts at the door jamb and/or shorts to the chassis.