ac versus dc fuses

In a home A.C. electrical system you have a 15 amp fuse protecting 14 gauge wiring, a 20 amp fuse for 12 gauge wiring, and a 30 amp fuse for 10 gauge wiring. It seems to me when I buy items for 12 volt D.C. automotive use they have, for instance ... a 35 amp fuse protecting a 16 gauge wire to power a tire compressor or a 18 gauge wire for backup lamps protected by a 15 amp inline fuse. I always believed the cross sectional diameter of the wire determined how many amps it could safely carry, (#14 wire = 15 amps) regardless if it was a 120 volt A.C. or 12 volt D.C. application. Am I wrong ??   Dan.

Except that DC is carrying a constant higher amperage, the lower the voltage, the higher the current.  All trucks here from 7.5 tons and up carry 24 vdc systems, (with droppers for radio, phones etc.), the relevant amperages for everything in the fuse boxes are about 2/3 the value of a car's equivalent.

"howie II" ... That would make my examples even worst. Dan.

No the higher the voltage, the lower the current carried and therefore the lower fuse value required, Ohm's Law. domestic cables are generally thicker because they a) have to last longer and b) transfer the electricity further.