The engine of your Ford runs through the use of an electrical generator known as an alternator. The alternator recharges the battery of your car or truck when the power is on and keeps the electrical system running. If the alternator fails, the vehicle will shut off because the battery will no longer hold a charge and thus there is no electrical current. If your alternator stops working, it is a good idea to test it first to make sure the problem is electrical before replacing it.
Park your Ford vehicle on a flat area and set the parking brake. Start the engine of the vehicle and open the hood to expose the engine. Take the digital multimeter and set the dial to the DC volts setting, since the alternator of the vehicle puts out direct current, not alternating current.
Place the negative lead of the multimeter onto the negative terminal of the battery, which is indicated by a negative symbol and a black cable. Place the positive lead of the multimeter onto the nut that holds the electrical cable routing to the alternator, which is marked by a red cable leading from the battery.
Check the digital display of the multimeter and make sure the current reading is between 13.7 and 14.7 volts for a properly working alternator. Understand that anything less than that indicates a problem and the alternator may need to be replaced. Ensure that the electrical connector is attached to the alternator firmly--this connector runs electrical current through the field windings of the alternator itself; check it by attaching the positive lead of the multimeter. Look for a 12-volt reading, as anything less is indicative of a failure with the internal parts.
Diagnose the alternator with the readings from the multimeter. A 12-volt reading from the connector coupled with a reading of less than 13.7 volts on the alternator itself indicates a bad alternator that needs to be replaced, while a 12-volt reading on the connector plus a reading between 13.7 and 14.7 volts on the alternator means the alternator itself is good, and the problems you are having with electrical current can be attributed to the electrical wiring of your Ford.
