My super-duper fan controller magic box!

[davepl]

I'm installing an eRod engine, and GM "simplifies" the fan contol by tying the two independent fan control wires together on a single relay. Since I have dual fans, I wanted discrete control. I split the wires out of the fusebox and then built my own 3-relan fan controller.

Why 3 wire?

With HI and LO control, allows you to have these states:

No fans
Both fans at 6V
One fan at 12V
Two fans at 12V

The point being the ideally it spends most of its time running both fans in 6V mode (12V but in series).

Here's the inside and outside of the project box. If anyone wants to duplicate it, it's basically the stock wiring setup that came in the older F-bodies, so there schematic is out there for that.