Having trouble

See the aux fuse in diagram, check that fuse for voltage, hot all the time, use a test light to check for voltage. Usually with spade type fuses, there is bare spot over each leg, don't need to pull fuse, to check for voltage. You see the other fuses besides the aux fuse in diagram, they all get voltage from the same source, so if they have voltage and the aux doesn't, something wrong with fuse box/wiring. Anything electrical always check voltage and ground circuits. Some of the national brand autostores will have an aux power outlet, You wire it up yourself and mount it, anywhere you want, under the dash, just one possibility. It kinda looks like a cigar lighter socket with a mounting bracket.