I have a 99 Volvo S70 with lots of highway miles. My headlights are so weak, sometimes at night I can barely tell they are on. Is it just a matter of stronger low beam bulbs (if they are available) or do I need to replace the headlight covers? Or something else?
Plastic headlights become pitted and hazy after a while. There are kits for restoring them available at auto parts stores. Basically, you wet-sand them with increasingly finer grades of sandpaper and finish with a plastic polish.
If youe buls are the originals, they are probably dimmer than when new. You can also try some brighter ones (I was very satisfied with Sylvania SilverStars; others will say they are worthless), but avoid higher wattage bulbs: They can overload the circuitry.
How does the car crank in the morning (Or whenever you start it for the first time of the day)? If it cranks slowly then the alternator is going bad. The headlights run off of the alternator. If you have a weak alternator then the bulbs aren’t going to get all the current they need, and the battery isn’t fully charging. Have an honest shop check the voltage output of your alternator. Anything less then 13 volts means that you have an alternator going out.
Cranks fine, starts up right away. Runs very good despite 163K miles.
Check the ground connections for the headlights. Poor connections (dirty/corroded) can cause the lights to be dim.