How do I adjust headlights on 1998 Mountaineer

Question edited for clarity.

Fuses 4 and 8, but there is also a relay involved.

Fuse Box Diagram Mercury Mountaineer (1997-2001)

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Here you will find fuse box diagrams of Mercury Mountaineer 1997, 1998, 1999, 2000 and 2001, get information about the location of the fuse panels inside ...

Mercury Mountaineer (1997 - 2001) - fuse box diagram

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Aug 11, 2018 - Mercury Mountaineer (1997 - 2001) - fuse box diagram. Year of production: 1997, 1998, 1999, 2000, 2001. Passenger compartment fuse panel.

Mountaineer » Fuse Diagram

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Fuse Box Diagram Mercury Mountaineer; engine 4.0 L Cologne V6 and 5.0 L Windsor V8 (1996, 1997, 1998, 1999, 2000, 2001)

Do you mean the whole headlight assembly or just the bulbs? If just the bulbs it is in the owner's manual. If you do not have an owners manuals you can download one for free from the Ford site in pdf format by clicking HERE

Get your Alternator and Battery checked. Autozone and Oreillys, to name a few places, will check them for free.

Your truck is 12+ years old, some of the plastic in the lens could be clouded. There are kits to repolish the lens.

If those ideas fail to help, pull the sockets and check for 12 volts at the bulb. If you are not getting 12 volts, ask the Autoparts place if your truck has a separate headlight relay.

according to the book, you have sealed beams--one piece:
To Replace:

• Remove the headlight bezel retaining screws. Remove the bezel. If necessary, disconnect the turn signal lamp wires.
• Remove the retaining ring screws from one or both lights.
• Remove the retaining rings.
• Remove the light from the housing. Disconnect the wiring connector from the back of the light.
• Push the wiring connector onto the prongs at the rear of the new light.
• Place the new light in the headlight housing. Position it so the embossed number in the light lens is on the top.
• Place the retaining ring over the light and install the retaining ring screws. Tighten them slightly.
• Check the aim of the headlight and adjust it, if necessary.
• Install the headlight bezel. Secure it with the retaining screws.
• Connect the turn signal lamp wiring (if it was disconnected).

bad ground with the dim headlight ck the headlight ground in that area

Test the leads to the bulbs while the low beams are on and then when the brights are on. If you have good bulbs & fuses with no power on low, the problem is most likely the bright/dim switch.
Not exactly sure of the Acura layout, but the covers over the steering shaft should remove with several screws to allow access to the switch (usually the turn signals are also the bright/dim switch) Test the leads out to the headlights from the bright/dim switch, that will tell you if the switch is bad.
Airbags are closely involved with this removal/replacement, it is NOT recommended for a amatuer to undertake.

Any mechanic can aim your headlights for you , but I would consider buying new bulbs. Even if your car has halogens , they do become less bright over time.
Some of the new bulbs on the market will light up 2 to 3 times as far as older halogens.

Is the focus of the headlight incorrect and should be adjusted?
Have you checked the reflective surfaces to ensure they are clean and the headlight glass is clean?
And finally - maybe the other bulb is of higher quality/light output. I notice a significant difference between different brands of bulbs sometimes.

Look under the hood.
There is a large relay which should have some info about lights on it.
I had this exact problem with my dodge ram

This is cuased by the multifuntion switch that is located on the steering column. It is the swith with the headlight dimmers on it.

You just need to remove the steering column bezels and replace the multifunction switch.