front brakes lock up

I think there's some water in the brake fluid. I don't know what the A/C has to do with it. The water could get hot and produce steam, the pressure of which would be felt in the pedal and lock up the brakes. Flush the brake system completely and see if that helps. If you want to find a specialist, here's a directory link for you: https://repairpal.com/subaru-repair-in-littleton-colorado