I've recently had similar braking , 850 N/A wagon that's been sitting for about a year at my pops. I found a busted fuse that was ringing the door open chime ALWAYS. As I was checking each fuse one of them didn't light up, it wasn't broken, but not green lighting, so after that I decided to changed ...

It could be the heater core. I'm pretty sure that's the only thing coming through the firewall that has water in it. I noticed the same thing then noticed the coolant level was low. Fist I vacuumed the carpet, then I put in straight water and placed newspaper on floor. Sure enough, I had a puddle ...