Interesting piece of Trivia.
I had a front halogen bulb going dim on the
1990 Silhouette, which has a four bulb front system.
(two outers, low beam....two inners high beam).
Replaced the bulbs and started checking things out.
At low beam the two outer lamps come on
At high beam the two inner lamps come on (and the outer ones are off).
It's a two wire system... each switch handles V+ to a different set of lamps.
So, I checked three GM cars
1990 Olds Silhouette Mini-Van
1992 Chevy Lumina APV
2002 Chevy Monte Carlo LS
And, (believe it or not), on all cars, the low beam calls for
one set of two lamps. The high beam calls only for the other
set of two.
otoh my friends 1994 Buick Regal uses a four lamp system and when
using high beams all four lamps are lit !!!
Why would GM use two different headlight systems???
To convert this to a 4 light high beam system all I would
need to do it jumper hot from the high beams to the low beams using
a diode and quick connect coupler. Is this thinking correct ??