Ok guys,
I was trying to stay out of this one (its hard to dispel preconceptions) but what some of you have been suggesting is inadvisable to say the least. Any modification to the headlights and their circuitry should not be approached with a cavalier attitude. These are safety devices and therefore effects not only your own safety, but the safety of everyone else in your vehicle's vicinity! Pushing more voltage and current through the circuitry will not only shorten the life of the bulbs but (in most systems) also the switch. If you blow a bulb, you have another to fall back on. If you burn out the switch, you will lose both headlights!! Not the thing you want to do on a dark, winding road! /ubbthreads/images/graemlins/icon15.gif
This is not to say that this is undoable. On the contrary, but one has to realize the limitations. Number one, the wiring and switching is typically designed around a 10A load for low beams and another 10A load for high beams (you can throw in a 10% fudge factor, the engineers like to take in considerations such as corroded connectors). The work-around for this is to relay the circuits. With this approach, the main current to the lights is drawn directly off of the battery (or the main engine compartment fuse block), through the secondary side of a relay. The wiring to the headlights is replace with wire 2-4 AWG larger than stock (depending on the stock wiring size and the wattage rating of the desired bulbs) and the headlight connectors are either modified or replaced with connectors that can accept the larger gauge wiring. Always use wiring with a high strand count and high temperature insulation (engine compartments are hostile environments and this is not an area for cost cutting). Careful routing is advised and also remember to fuse both of the new circuits. The relays are controlled by the stock headlight circuitry, wired to the primary side of the relays. On domestic and most imports, this will require one relay for low beams and one relay for high beams. Cars that are wired for DIN specifications (German) will require 2 relays for each beam, as the individual headlights are on separate circuits (good ol' German redundancy /ubbthreads/images/graemlins/wink.gif ). It is highly advisable to obtain the appropriate wiring schematics for the vehicle, as I'm only dealing with generalizations here. To this I would like to add, if for some reason one feels that one cannot do this job with a high degree of professionalism, then leave this job to professionals.
Allow me to close with thoughts on brightness and aim. Remember, you share the road with others and blinding oncoming traffic is not only annoying, but hazardous. Use a reasonable wattage for your low beams, close to the stock wattage. As to aim, a 3" drop of the projected beam centers at 30 feet (for the low beams) is acceptable in most states (check with your local DMV). The lateral aim is generally straight ahead or skewed slightly to the right (once again, check with you local DMV). In the end, if you still find that your headlight beams are less than desirable (as is the case with most DOT approved headlights), consider auxiliary lighting. 'Nuff said.
Dan
ASE Master Mechanic 1982-2000
P.S. I should also note, being as most headlights now days are plastic and are quite capable of melting, should one install too high of a wattage bulb. Proceed cautiously. /ubbthreads/images/graemlins/thumbsup.gif
