check the bulb in the headlight that is not working if it is fine test your wires to make sure it is not shorted out some wear
2011 Dodge Ram 1500 headlight bulb replacement: Purchase the correct replacement headlight bulb(s) first, before disassembling the vehicle. Then consult your owner's manual for the headlight bulb replacement procedure. As simple as it sounds, the owner's manual is the best place to start for bulb replacement instructions and illustrations. You may want to consider replacing both left and right at the same time in order to keep brightness and color equal (optional).
changing the bulb
9004
Yes , according to the 1998 Mercury Mountaineer Owner Guide : ( the headlight bulb is # 9007 )
9004
the headlight assembly needs to come out in order to replace the bulb.
This is probably a 9004 halogen bulb but to be sure just go to your local parts store and tell them that you need a new headlight bulb for a 1998 Jeep Cherokee.
You have to remove some screws and then pull the headlight assembly out of its place. it is held in with a clip after all the screws are removed.
the headlight assembly needs to come out in order to change the bulb ive had to do that to my 98 as well.
9007
drop the bumper and take the headlight housing out