I've searched the archives and haven't found anything on this. I don't know how much of the following is relevant, but here's everything that happened leading up to the heater spontaneously coming on:
1. We haven't used the heater in months.
2. We had to brake REALLY hard coming off the freeway, like if we had been doing a 60-0 test or something.
3. We drove up a steep hill.
4. We turned the car off at our destination.
About 20 minutes later, we got back in the car to drive home. At this point, heat started coming out the vents. We monkeyed with the heater controls to try to get it to turn off, but that didn't work. The heat is coming out on both sides of the car, and all the vents (windshield, dashboard, floor, etc.).
Yeah, ok, we can close all the vents and open the windows, but a little heat still seeps out.
Thank you for your help.
Santa Barbara, CA