Originally Posted by 99DangerRanger
It's only one bulb. A dual filament, so in order to have a low beam and a high beam at once, which makes no sense, you would need to seperate housing with different bulbs. Now If you're talking about the fog lights I think that someone did a How-To for 2004 and up. Search "Fog Light Mod" and you should find what I think you're looking for.
Actually with a diode acting as a 1 way check valve or a 5 pin relay, you could make both filaments burn at the same time. To use a diode, you would simply splice in a jumper wire from the high beam wire to the low beam wire with the diode in it. That way when you turn the low beams on it only powers the low beams because the diode prevents the power from going to the high beams. When you power the high beams the power also goes to the low beam. The problem with this is that you will have a significant change in amperage draw when both are on and I don't know if the stock wiring could handle it.
To use the relay method, get into the wiring harness before it splits to the individual bulbs. Cut the low beam wire and put female spade connectors on the ends. The wire that goes TO the headlights plugs in to the 30 pin, the other wire you cut goes to the 87A pin, splice a wire from the high beam wire and connect it to the 85 pin, ground the 86 pin, and run a constant hot from the battery, through an appropriate fuse, to the 87 pin.
How this works is with just the low beams on the relay is not energized and will stay in it's default position, the low beams will work like normal because the connection is closed between the 87A and 30 pins. When you turn on the high beams, the relay is energized by the current from the high beam wire and power will be pulled from the battery, through the now closed connection between the 87 and 30 pins, to the low beams. You are drawing power from 2 "different" sources at different times.
If this is advisable or not, I don't know, I wouldn't do it but I already have 80w low beams and 100w high beams vs. stock 55w lows and 65w highs. I could see heat being an issue.