You wouldn't change these voltages in a car. Please be more specific.
depends on voltage.... 120volt = 8.33 amps , 240volt = 4.17 amps
The difference between a 120 volt and a 240 volt is one has more power. Volts are the power that comes from a battery.
Run a new and much larger 3 wire line to the outlet and replace the 110 outlet with a 220 type outlet that matches your new air conditioner.
Your neutral May not be grounded good
NO. Don't try it. Some are designed to work on either, some aren't. If it won't work on 120v, it won't work on 240v.