Hi!

I just bought a set of high-wattage halogen bulbs for my 1976 w123 200D. I have the 'newer' version rectangular headlight assembly (the original was the one with the big round lamp for the headlights and a small round on for the fog lights, but also in a single unit). Problem is, there wasn't much of a difference as regards brightness. I was told that this is because my car model was not equipped with headlight relays. What EXACTLY are relays and how will it help brighten the headlights? Is one relay just good as another or are there "specific" relays (one kind for headlights, another kind for the aux. fan)? How do I install one (hope it is a DIYer)? Thanks in advance!