i have a computer fan with a yellow, red and black wire. where do i connect the yellow wire to!? is it possible to connect a computer fan to a car? thanks

 

I believe most computer fans are 12v...all you need to do is just hook it up to a switched power source. Don't use your amp's power line - you may introduce noise into your system. Dont ground with any audio equipment either (for the same reason).

One way to hook it up:
Use your HU's remote lead to control a power relay. Grab a power input (which is always +12v) for the relay from the fuse box or directly from the battery. The relay's power output will go to the fan. This will make the fans go on anytime the HU is on.

Alternative:
Instead of using HU remote lead, use a factory lead that is only on when the car is running to turn on the relay (fans on whenever car is running). On top of that, you can put an inline switch so you can turn it off and on whenever you want (assuming car is running).

You should only need to hook up the red and black leads on the fan. The yellow won't be used. Just cut off the plug and touch the leads to your car battery to figure out which ones. I use computer fans all the time in my amp racks. They have 4-pin pigtail harnesses for plugging into the computer wiring, but the fans themselves only tap into 2 of the wires (red and black). What size fan are you using? Is it a standard 4" fan?