What's this little black box?

Does your car have the shark fin antenna? If you don't it might be a radio antenna.

 

It's got a shark fin - I presume an antenna.

 

My plain Three model only has the little skinny box, to the left in your photo. And no exposed wires, or wires imbedded in the windshield. Thanks for the nice pictures. I wonder how do you know when that little box is working? Does the AC have to be turned on? And does the AC have to be in the auto mode? I've never seen anything different happen in my car.

(Many Prius owners don't like to run the AC. They may never know if the humidity/fog feature is working or not.)

 

Yep, we all got the "Jaws fin" on top... You can see mine in the picture.

 

No idea - I thought it would be in AUTO mode.

 

Here's a guess for you:

Have you ever noticed that if you set your climate control to Auto, that under certain circumstances, it will change from delivering the air flow to the floor vents only to a mix of the floor vents AND the defroster? My guess is that this sensor plays a role in that decision.

My guess (I don't monitor the A/C current with a scan gauge, but it could be used to confirm) is that when the above happens, the compressor is activated to dry (reduce the humidity level) of the air. (I believe that this also happens when we press the Defrost button).

Just a guess, but fairly consistent with observed behavior...

 

I do not have that on my Trim Two. Just the black dots.

 

Hmm, I got those straight wires in the screen like Alan, but never remember to look for the little black box!

 

I have the US base model. That may be the difference. Perhaps somebody with a US Trim 3 or 4 can check.