I wanted to share my new found fan control circuit thanx to fellow member Matt400. I was searching forums on transmission cooling and Matt posted his ideas on how he wired the viscous fan to come on at drivers discretion. I have an 05 and I used a 1k ohm potentiometer to fool the computer into turning the fan on. It turns out that my fan doesn't engage until 218 degrees. I like that I can manually engage the fan now to come on during slow reverse driving, long hard pulling up hills or when the trans temps are higher than I like. The only side effect that I can find is the compter raise the idle speed when in park to about 1000. May not be a bad thing here in Arizona when I leave the truck idling for a few minutes. BTW, Matt used a 180 ohm resistor for his 03 and mine turned out to be 500 ohm to simulate 225 degree coolant temps.