I have a 2011 F450 pickup that came with the upfitter switches. I found the wires for the switches and they all look to be 16 gage. Looking at the on line literature, it says that switches 1 and 2 are 25 amp, 3 is 10 amp, 4 is 15 amp. It shows that they all go through a relay. Are they really only using 16 gage wire for a 25 amp curcuit?

 

The power goes through the relay. The wiring you're seeing is just used to trigger the relay, not provide current. You don't need 25 amps to trip a relay.

 

If your truck came with the Upfitter switches installed, you will have 4 blunt cut wires taped to the main harness going through the firewall. If you or someone else installed the Upfitter switches as an add-on, there should be 4 blunt cut wires in the area near the relay box. Here is the infor on installing the kit.

https://www.fleet.ford.com/truckbbas...tml/Q157R3.pdf

There is a photo in the bulletin that shows the blunt cut wires.

https://www.fleet.ford.com/truckbbas...tml/Q180R3.pdf

 

I dif some mote reserch. The 4 blunt wires from the outfitter switches are under the dash, left of the steering column. They are 16 gage wires and are proteted by fuses. Switch 1 and 2 ARE protected by an 25 amp fuse. 3 is 10 amp fuse, 4 is 15 amp fuse. So rated loads are about 20 amp 1 and 2, 7 amp for 3 and 10amp for 4.
they all controlld by a relay.
It looks like the E series wites fo end up under the hood, the F series are under the dash and are NOT connected to the pass through wires.
there are a few charts from the SAE and 16 gage wire can be used on 25 amp circuits if the wire is less that 3 feet.