I had a problem with my 04 that in the winter time my car wouldn't want to start using a charger and it didn't start even though the battery was good only way I could get it to start was with with a jump from a BMW in my other carI just read some threads on this forum from back in '04, it seems the dimming lights problem was normal on these cars even when new.
Has anyone ever fixed this issue? Are there members here that don't have their headlights dim when they hit the brake pedal? Every bulb, interior and exterior, on my '01 dims when I hit the brakes, or even use my turn signals.
My OB has a brand new battery, and the alternator was replaced about a year ago. Clean terminals, all of the grounds I've seen look fine and have been unbolted/reattached.
If there is an alternator available that is higher output, or has a better voltage regulator that will solve this problem, I am all ears.
Back in '04 a Canadian member found that all of the new Legacy/Outback models on his dealer's lot exhibited this same problem. I am hoping that since then, a better alternator or a homebrew fix has been developed to remedy this. When tapping the gas pedal, all of the lights brighten, so it is obviously an issue with the charging system being inadequate at idle by design.
I did the whole cleaning round bits and I actually added grounds didn't really help
I finally found out what it was it was the terminal negative terminal on a battery cable bad crimp on the terminal I bought a couple new ones from Amazon brass terminals replaced it then noticed no more problems at all starting the car and then also the lights look much brighter than before so that might help you out