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The Fitech efi system offers a black wire that allows for a programmable bump in rpm’s with compressor activation also offers a yellow wire with a programmable electric fan activation at a pre-set coolant temperature...

I have been using the yellow wire to trigger a fan relay and it works great. Now I’m trying to get the black wire to do its job but I need an A/C ground and I am not sure where to find one. I see that the A/C binary switch can be replaced with a trinary that will send a ground signal but it makes sense that I should also tie it into the fan relay to activate the fan as well...

If I just tie the grounds together I’m afraid that I will bump my rpm’s upward every time the electric fan comes on...which would be ok but no ideal.

Has anyone recently tackled this idea ...?
Since the compressor clutch is engaged by sending power to it you can add a power-switched Bosch-type relay to its circuit that will give your FiTech system a ground signal. You'd wire it like so...
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