I have a question.....In the FAQ's there is a section with a question that asks "can the fans be rigged to come on without the engine running?", and it goes on to say about splicing a wire off the coolant sensor in the pass. side head...etc.....My question is, can you use this same setup while the engine IS running???? or would it mess something up? I thought about buying a hayden fan turn on relay, but they seem pretty complicated and there are alot of wires you have to splice into. Any info would be great....Im stumped...

 

Unless I'm wrong the wire from the relay to the switch in the block is basically a ground wire. When the engine temp gets to the right point, the switch closes and due to the ground it just created, the relay supplies power to the fan. You can splice into that wire and run a wire to a switch on/under the dash (run the wire from the other side of the switch to a good grounding point under the dash or in the console) and use the switch to turn the fan on whenever you want. By splicing into the existing wire, the GM temp switch still works.