Headlight wiring

[justasquid]

You could run a relay, so when you switch your highbeam on, it also supplies power to the low beam side.

But I would just bypass the dimmer switch all together for the low beam. What happens is your low beam wire looses power from the switch itself. Basically, you have to intercept the power leading to the dimmer switch, splice into that wire and run your low beam from that wire. Keep power going to the switch though, the only difference is the low beam will no longer be coming from the switch, just the high beam will be. It will no longer switch power between the high and low, it will be an on off switch for the high beam.

[justasquid]

here is a really crappy paint program to show what I mean. Also, you may want to just use the lead in wire as a signal wire to an additional relay. That way, you know you have the full 12v power, and not just a spliced power to the headlight.