Decade and a half ago, I added 4 relays to my set up. At the time it was to handle the current required for high output Hella QI units -- but it has contributed to the longevity of the stock components by significantly reducing the current they see. Low beams are on separate relays on each side, high beams on separate relays each side. Relays are 'triggered' by input from the Volvo headlight wiring. Doesn't impact the bulb-out indicator function. And, if you're careful with your wire length/sizing - you can deliver significantly more voltage to the filaments than the stock Volvo system does resulting in significantly brighter lights.

Nice tutorial here -- http://www.danielsternlighting.com/tech/relays/relays.html
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82 242 6.2L coming...; '15 Honda Fit