Just a couple of days ago two lights on our otherwise flawless subaru popped on at the same time. The battery light and the brake light both came on at the same time. When the car is cold they both turn off when idling but come on when at speed. When the car is warmed up they both stay on.

 

I am looking for ideas on a cause (someone suggested the alternator)....

alternator.

 

go have the charging system tested at autozone or some other auto parts store.

 

Have them test both the alternator and battery.

(someone suggested the alternator)....

They are probably correct...