How would I go about getting the fans to turn on at a certain temp.

 

Im not too keen on your pcm but there might be a way for you computer to control it, if not they do make thermostat kits, and theres always the option of a switch to control it, but that can get dangerous if your absent minded.

 

If you get the flex a lite fans...they come with their own module and you can control with its unit.