Game where you guess what it is from a photograph with a tiny field of view, solution

Raven figured it out on his first guess, although Rob Williams ran across it too in his fusillade of responses.

The two copper prong things bridge a grounding plate and one of three fan speed lines. The big black piece you see in the first photograph really is just a big piece of plastic. The arm controls both the vent position and the blower motor: the first half of the travel moves the vent from 0% open to 100%, and the second half turns the fan up.

I cleaned the whole thing up yesterday (including repairing the busted vent control arm) and the results are at right. You'll notice that the rightmost fan contact has some melty plastic around it¹—I'm guessing that at some point, the connection with this pad became so corroded that the resistance between the pad and contact caused the pad to heat, which made it fall into the plastic until it wasn't moving current any more. I'm sure that smelled awesome.

¹ maybe it's easier to see in this shot, which I took before cleaning everything up.