Rewiring horn and wiper motor for 12 volts

[Badpuppy]

You need to double the number of turns to get the same current. Flux density is a function of field current. You can use a slightly smaller wire gauge so it fits. Much easier to use a 1.2 ohm 50 watt resistor in series. More efficient to use a 12/6V 10A reducer if you can find one, and that can work with positive ground.