Cadillac Repair: fuse problems, fuse problems, spare fuses

Question
i check the fuses by looking at them and they look good but when i try the light tester on them when they're in place there is no response all the other fuses seem to be good exept two of them 1 and 25 (first and last) on a 1991 cadillac sedan deville, what can be causing no power to these fuses

Answer
fuse #25 you must have the parking lights or head lights ON and are you positive that you are testing fuse #1 and not fuse #2? Because fuse #2 & fuse # 3 are spare fuses and do not have voltage on either side of the fuse.

Fuse # 1 will ONLY have battery voltage on both sides when the engine is running or the ignition switch is in the ON position.