I am trying to install a Trans Temp, Differential Temp and Clock on a Pillar Mount. The question is which fuse location is the one that dims the interior gauges when you switch on the headlights and is there any way to include my clock on that same fuse? In other words is that fuse hot all the time?

The truck is a 2001 F-250 Super Duty Crew Cab

 

I looked it up, and there is no fuse that you could tap into and get the dimming feature. The circuit is fused, and then goes through the dimmer in the headlight switch, and then feeds all the lamps. What you will have to do is search under the dash till you find a lightblue/red wire. All the lightblue/red wires feed the illumination bulbs, and the lightblue/red will have the dimming feature, so just skin some insulation back and tap into one of these wires, or get an official tap and crimp it into the wire.

By the way, while I was looking at this circuit, I discovered they no longer use the variable resistor in the headlight switch for this feature. They now have a electronic module in the headlight switch that uses pulse width modulation to make the lights dim or brighter.