This fan mounts to the interior side of the roof of the 300ZX, under the same finisher panel that houses the map lights. It circulates ambient air around a temp sensor to get an accurate reading on the cabin temperature. When it goes bad, it will often make noise or seize completely. Once it stops functioning, the climate control system will no longer get an accurate reading on cabin temperature, and will fail to regulate the blower fan speed automatically, often resulting in the fan staying on full-blast even when the cabin temp gets way below or way above the set target temp.