Ford Mercury Villager 1997 Owner's Manual page 273

To avoid damaging your vehicle or your battery, and to avoid
injury to yourself, follow these directions for preparing your vehicle
to jump-start and connecting the jumper cables in the order
they are given. If in doubt, call for road service.
Preparing Your Vehicle
1. Your vehicle has a 12-volt starting system, so you need to use
a 12-volt jumper system. You will damage your starting
motor, ignition system, and other electrical parts if you connect
them to a 24-volt power supply (either two 12-volt batteries
in series or a 24-volt generator set).
2. Do not disconnect the battery of the disabled vehicle. You
could damage the vehicle's electrical system.
3. Park the booster vehicle close to the hood of the disabled
vehicle. Make sure the vehicles do not touch each other. Set the
parking brake on both vehicles and stay clear of the engine
cooling fan and other moving parts.
4. Check all battery terminals and remove any excessive
corrosion before you attach the jumper cables.
5. Turn on the heater blower in both vehicles. Turn off all other
switches and lights in both vehicles to prevent possible
damage to either vehicle's electrical systems.
Roadside Emergencies
269