1989 Pontiac 6000 Cooling Fan Won't Come On!!

I've tried everything i could think of! i tested the fan itself, it ran (so it's not the motor or the fan itself). It has plenty of coolant. I swapped some of the relays, still nothing (not a relay problem). I changed the temp. sensor and switch, still nothing. I even checked all the wires going to it. They all checked out ok. I run the car idle to see if the fan kicks on, but it gets to the point steam begins to come out, and the the upper radiator hose willl take your skin off if you touch it. Any suggestions for this, i'm trying to advoid a taking it to a garage.