In Reply to: can the e34 wiring system handle higher watt bulbs posted by r o b on December 23, 1999 at 20:03:36:
Many have gone the higher wattage route with out toasting the headlamp switch or wires BUT by adding a nice set of relays and some 10g and 12g wire you can get 20% more light out of your existing setup. Think what this does for 100w or 120 w bulbs.
If you are sticking with stock wiring 100w high and 70w lows are a very safe bet. The wiring with relays is fairly easy and intuitive. I solder and heat shrink everything now as I once had a ground connection go bad and could diagnose the problem. Wrap everything in that plastic wire loom stuff and you have a factory looking job. This URL should be very helpful. http://lighting.mbz.org/tech/how_to/relays/
Jeff Donnelly, 540 with 560 watts of projected light