Quote:
Originally Posted by MotoWells
Thank you, with my setup I do have two fans however the GM Controller I have has one wire. GM said to attach that single wire from their relay / fuse box to the fan. I pigtailed that to drive both 12 inch fans and ground both directly to battery.
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This is often true. On the GMPP LS3 controller, for example, the wiring harness they give you has the two fans (blue and green wires, if I recall correctly) tied together so that it's just one output.
I went into my harness and split the wires and then into the code and split the ON temps, but some harnesses come with them bundled together, which is fine, you just treat them like one fan.
So ignore my stuff about HI/LO and split operation - your fan should come on at 207 (or whatever) at FULL speed.
Just as a random though - the later ones, like the LT1 and LT4, use a PWM (pulse width modulation) fan control scheme, meaning they use a high power transistor and they turn the fan motor off and on a hundred time s a second (or whatever) to give them speed control. That wouldn't work through another relay, so if you had that setup (and I do not know which you have), you couldn't use an additional relay, you'd need to use the wire from the ECM. I only mention it because some people use the fan control wire to trigger another relay, which doesn't work with PWM. But that's only on the fairly newest ECMs I think.