Hi guys i have a 89 gta 5.7 with dual fans. The fans kick on like there suppose to, but i would like to have the choice to control both manually. I am interested in installing a manual fan switch. However i would also like for my car to operate as gm intended. What is the easiest way to add a manual fan switch, for BOTH fans? I have been studying the chilton, & chevy thunder wiring diagrams. I would like to tap into the wire as close to the ecm as possible. Is C1, or E8 the wires I need to tap? looks like E8 will work only for the primary fan. any help would be great. btw I don't even see C1 on my chilton diagram.

i believe the primary fan works of the fan switch, the other off the ac.

If you install a switch in parallel with the fan switch wire, you will be able to turn that fan on if you want to and it will still function as the factory intended as well. The switch will have to go to ground as the factory fan switch is a grounding switch.

I dont know about the secondary fan, i've never dealt with one.