I recently had the heater control module replced on my 2003 HCH. Although the repair was not too expensive ($350), I was amazed at how many things this board controls. Basically, the problem started when I accidently hit a speed bump way too hard. All of the sudden, the lights on the heat/AC knobs went out and the heat came on -- full blast! Soon my car was nearly 90 degrees on the inside.

As if that wasn't bad enough, the defogger mode was non-operational and the rear-window defogger was also offline. The idle-stop no longer triggered at stops either. Of course, the fan blower cranked so hard that the IMA battery kept draining down to 1 or 2 bars, which would trigger a forced recharge. That did *wonders* for my fuel economy (not!)

Well... The car's fixed now and it's back to the usual 42-45 MPG.

Funny thing about my car: as the vehicle has aged, only the CITY mileage has decreased. When I visit my mom and to that 3-hour straight shot on Route 70, I can usually get 47-51 MPG just like when it was new.