I have an 05 manual, speaking as a construction Electrician, start with the 5 amp , if she pops try the 10 amp then try the 15 amp. I cant see MB/Chrysler/ Karmann changing the wiring harness,to suit a year or style and the fuse is to Protect the wiring and not the device that is being used. Without digging into the wiring harness I would think that 16 gauge wire would be a minimum, and that should be good for 12 amps, go figure