Dual Filament Head Light Function

[CBDZ]

I'm wiring my buggy. I'm not using any VW style switches, so I've got options on how to wire things. My question is should I wire the headlamps so the low beam filiments stay lit when the high beams are on, or should only one be lit at a time?

[Piledriver]

I suspect that will greatly reduce the life of the headlamps if set to run both filaments on for any extended period.
(is useful for a quick flash)

Note that decent H4s running via a good relay with a fat power feed right off the battery will almost melt paint if you get close enough ... Huge improvement vs stock setup. Use the switches to control the relays, only.

[Ol'fogasaurus]

You can do both elements but I would not recommend it mainly for the reasons Pile said. Remember, the each of the elements are putting out a lot of heat so with both elements turned on you are probably not doubling the amount of heat but close to it. You can wire the flashing bit like cars do now day just as Pile said which, for on the street, is not a bad idea. You will want to use a CB or fuse and relay for wiring protection and be sure to accommodate for the length of the run (voltage drop: http://www.calculator.net/voltage-drop-calculator.html and wire size: http://www.powerstream.com/Wire_Size.htm). You can wire them to operate "hot", through the ignition or a separate switch

The stock relay can be used of even a foot operated relay could be used. Most of the relays have the input pin marked and the high and low beam pins marked.

I hope this helps.