4-Hi Headlamp Relay

In practice, in a vehicle where some lamps dim or go off when others become bright such as when an indicator is switched on etc......is nearly always due to one problem, and that is an earthing fault. Finding the loose earth wire, perhaps in a connector under the dashboard etc is likely to solve the problem.

Another common place to look for an earth fault is where a wire is screwed in to the metal body of the car and the screw connection is rusty. This is often close to a bulb, eg near the rear tail lights etc. The metal bodywork is often used instead of an earth wire (if the bodywork is metal) and rusty connections are a common culprit for this problem of dimming bulbs.

http://everycircuit.com/circuit/5806245497274368

There was me thinking that you were trying to skirt around an earthing problem, whereby I now see that you are instead trying to obtain brighter headlights, so you can ignore my earlier replies.....I will leave them there though just in case anyone has such an earthing problem.

Back in the late 1960's I made the dimmer headlights stay on while the full beam was on in an old camper van....I just used switches to achieve that....it worked quite well for extra brightness. I had just dropped out of an electrical engineering apprenticeship after three years of training (the apprenticeship was a five year stretch in those days....nowadays I would have been classed as qualified after three years.....but such is life and it was the 1960s when it was cool to drop out and see the world). We lived in that camper and headed off down the beautiful Rhine and had a great time before returning home with no money and no job. Along the way cars coming the other way would flash us because our lights were blinding them (wrong angle for dipping etc).....so I disconnected the extra beams......great memories, stupid youth, ah well !