Hi, I wired in an aftermarket head unit and it was working fine through the speakers already in the car, but i hooked it up to some 6x9s today.
they worked until i turned them up and the stereo cut out, wouldnt come back on.
I then noticed a whirring and clicking noise happening when i turned the battery on. Im sure i have not heard this sound before.
the clicking comes from the part i have circled, the little metal bit kinda clicks up and down just once when then battery is turned on.
what is it? what does it do? should it be making that noise? i have a video of it happening i can upload if need be?

Would be very appreciative of any help offered.

EDIT: Here is the video. http://www.youtube.com/watch?v=Uo5Krt3xqac

Also, forgot to mention after the head unit stopped working i put the old one back in which works fine.

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Your intake looks completely different than the one on my '94 e320 so I can't say I'm 100% sure, but mine made the exact same sound when I connected the battery. It appears to me that the Electronic Throttle Actuator (ETA) is adjusting and setting itself when you connect the power.

thanks for the info, after a bit of digging around i learned what that part was and the purpose it served, and i figured it was just setting itself when the power came on, but no one has been able to tell me for definite!

It may have been making that noise the whole time i have owned the car (only a week or so) and i only started noticing it after the head unit fiasco due to being paranoid i had damaged the electrics in the car somehow!