The best way to find out if your headlights are dimming is to turn your lights on when it's dark at your house and check and see. Also you can go to auto zone and ask if the lights in your car are dimming and what you can do to fix them.
If your vehicle has a voltometer, the power will be low. If not, you can usually tell by dimming of the headlights or other electrical systems
Need to know first if you have sealed beam headlights (those will have the single bulb with the dual filaments) or composite headlights (those will have two bulbs) in order to answer this question.
You can buy new headlights bulbs at www.amazon.com or www.pepboys.com Make sure you know what size bulb you need, however. If you want to go to a store, Wal-Mart always has bulbs
LED headlights are made out of a bunch of smaller bulbs, like Christmas tree lights instead of one larger bulb. You can find them at auto parts stores, and they are brighter.
First have you replaced the bulbs in it and there not working or do you need to know how to replace them
There is a parking brake headlight dimming switch some where in the system. You can find some info on it in your owners manual. My switch is also not working. When I find out more information I will let you know.
You should specify which bulb. As is, we don't know if you're talking about headlights, tail lights, or any other number of bulbs that vehicle requires.
The actual bulbs; yes. The headlight housings; I don't know. For bulb information, see sources and related links below.
Without knowing your sytem power requirements, how many amplifiers and how big they are, etc, it is hard to give a definitive answer. However, if your headlights dim on large bass hits, or worse yet are "dimming with the beat" then it's pretty safe to say that you do need a cap.
There are many bulbs on a vehicle, need to know which bulbs you want to change.
The 2004 Sorrento has a major problem blowing out taillights and headlights. The dealer said they found no problem but I have never had to change so many bulbs. The only thing I can guess is there is a grounding issue some where and techs now a days are just parts re placers and do not know how to trace problems.
Need to know the model. As is, you could be talking about a passenger car, or a tractor-trailer power unit. Generally, you just depress the tab in the bulb ballast on the backside of the headlamp assembly, twist counterclockwise, and it should come right out, allowing you to replace the bulbs. This is, of course, assuming your vehicle has composite headlights, and not sealed beam headlights.