help identify interior part
 

Have 87 300 zx turbo and can't find my owner's manual; probably wouldn't help anyway. There is a continuous loud buzzing noise coming from a part next to the interior map lights (those between the t-tops). It has a cover and after removing the cover, I can feel it vibrating and actually took out the screws holding it in but put them back when I couldn't tell what it went to. Noise stops when the car is turned off. Would like to know what the part is and what it controls. Any help appreciated.

climate control temp sensing fan.

Thanks for the quick reply. I'll check this out.