The important feature to look at when buying bulbs for Ford is voltage at 12 V. If you need new lights of turns in Explorer, choose only BA15S type of base. Proper functions of turn lights in Ford Explorer are needed for safe drive. Turn lights of Ford vehicles with 4.0 motor don’t need to be changed often. But with replacement of Explorer 4.0 turn lamp for 2001 vehicles needs good choice. Also for 1999 model year cars you’ll need exact nominal power of 21 W.
One of destroying factors is over 12 V voltage lamp and bulbs having more capacity than 21 W. Unless the cover glass in signal of Ford Explorer isn’t broken, you need to change only bulb. It’s better to buy BA15S base lamp to ensure that lights in 1999 Ford Explorer work properly.