i just changed all the coolant like three weeks ago

 

First off check the coolant level. Top off if necessary. Then open the hod and let the car run. As it comes up to normal temp watch to see if the fans kick on. Now If they do then there may be another problem I.E. clogged coolant passages, weak water pump, clogged radiator. Running both fans may keep it a little cooler BUT it's a temporary fix.

Now if you still want to run both the fans together I'll have to look at the wiring schematics and see how to do it. I can run my Conquest's fans at the same time by running a single jumper from one thermoswitch in my radiator to the other thermoswitch. But I'm not sure how the 4G63 or 420A engines determine temps for fan actuation.

 

You dont think you could get a leak? Check it.