Need Help With Technical Issue

[96chevy7.4L]

Hi I have a 99 chevrolet C3500 with 7.4L engine. I am trying to get the aux. engine cooling fan to come on sooner. On my 96 there was a cooling fan switch in which hypertech makes a switch to turn it on sooner. My 99 doesn't have that cooling fan switch just a cooling fan relay. Does the computer control the fan on this year. If so can it be changed in the computer to make the fan come on at a cooler temperature. Any help appreciated.

[L29er]

so you don`t mean the main (big) fan, the little on in front of the rad? is for the A/C condenser, not sure how to get it to run more unless you run a/c or defrost lots, it must be controlled by a thermostatic switch somewere though, i`ll check my factory manual when i get home tonight...maybe it can be modified (:

[L29er]

if you find your auxillary cooling fan relay (underhood) you could wire in a switched ground on the dark blue wire, according to the factory diagram the VCM (vehicle control module) grounds the dark blue wire to initiate the auxillary fan to operate. It doesn`t really describe what source it uses to figure when to turn on the fan but i`m wondering if it uses the temp sensor in the MAF sensor to determine outside air temps? dunno but this is an option to run it continuously, if you "T" into this wire if you leave your switch "off" it will still function as the VCM determines, and you can turn it on permenently any time the ignition is on...so your switch would be basically a "ON' or "AUTO" switch i guess....