The "Auto" It does huhzing! (Auto headlights never turn on)

I recently purchased a new to me 2012 Prius v Five. The "auto" setting on the headlight switch does not seem to do anything, no matter how dark the ambient environment (even out in the country with zero artificial lighting) -- the headlights turn on normally when turned to "on" and turn off normally after the car has been turned off for 30 seconds.

I wonder if it is tied to an issue with the sensor (the manual says that the sensor also affects the Auto A/C, which also appears to be acting funny -- it blows frigid air, no matter the setting, no matter the outside temperature, unless it's set to >85°F; this isn't a problem when it's 90°+ outside, but may be annoying in the winter.)

I'm trying to figure out where to start my troubleshooting, or if this is a known issue?

FYI: I'm new to Priuses (or is it Prii?), but am old hat at cars (first car was a '65 Mustang that I rebuilt, I've built and raced a SpecE30 race car and wrenched on my own daily drivers since I was a teenager); this 2012 is the most modern vehicle I've ever owned and the first non-manual transmission.

 

Just to update my very old post: the problem was the wiring harness inside the dash.

A few months into ownership, I experienced a hybrid pump failure and had the car serviced under warranty at the nearest Toyota dealer. They found evidence of rodent damage while the car had been sitting on the used dealer lot; they were able to correct the cabin temp sensor but not the auto headlights.

 

I'll dig through it -- thank you!

I'll admit that after posting asking for help and getting nothing more than "pay for TIS" I wasn't super enthused about the community here (and I was intimidated about working on the Prius, despite all my automotive repair experience). Since then, I've replaced the water pump, built a Techstream tool and done a lot of work on the car(s) myself, but not tried to tackle the wiring as the dealer made it sound awful (and wanted $2000 for the diagnostic work, alone).