2003 Subaru Forester ABS and Brake lights on constantly cas

Starting this past summer, my ABS and Break lights would come on spontaneously while driving. I was typically using the AC at the time and it would go OFF INSTANTANEOUSLY when these lights would come on. This happened on and off for about 4-6 weeks and then disappeared for several months. NOW, for about the past 4 weeks, the ABS and Break lights have been on CONSTANTLY (I am now totally unable to get them to go off) and therefore the heat does not come on at all. When I press the "auto" button to turn on the heat/cool system I do hear a 'click' but nothing happens.
I am begging you for some insight. The dealer keeps raking me over the coals and I am tired of $400-$600 repairs every time I go there...I am broke!
THANKS A MILLION FOR YOUR INSIGHT!