16 F350 Diesel.
My truck came with the Up-Fitter switches.
I understand ..
Switch (1) Yellow wire 25 amp
Switch (2) Green/Brown wire 25 amp
Switch (3) Violet/Green wire 10 amp
Switch (4) Brown wire 15 amp
I understand there are (4) wires that pass threw the firewall
A, Black/White wire
A, Grey/Red wire
A, White/Red wire
A, White wire
Now for the part I don't get, and I apologize
Switch (1) goes with which color pass threw wire ?
Switch (2) goes with which color pass threw wire ?
Switch (3) goes with which color pass threw wire ?
Switch (4) goes with which color pass threw wire ?

 

I think you can use any pass through wire you want. The colors just let you know what wire to use in the motor compartment. I have hooked up half dozen things on different duties and think I just "picked a wire".

 

You could use a test light or meter to determine which is which.

 

Yep - exactly what I did.

 

doesn't matter which pass through wire you use, as long as whatever you want powered by a particular switch is attached to the opposite end of that wire

 

The Pass Through wires are NOT connected to anything on either side of the firewall as delivered to the dealer. It is up to the owner to use the Pass Through Wires for anything they want. The owner will have to make connection to any of the 4 wires on each side of the firewall.

If you want to power a device/lights via AUX 1 switch, you will need to connect the AUX 1 colored wire to ONE of the colored Pass Through wires. Then in the engine compartment, you will attach the same colored Pass Through wire to the device/lights wiring you are wanting to power via the aux switch.

 

Yes. Even though I had a printout of some sort that someone on the forum recommended, that fact about the pass through wires not being connected to the upfitter switch wires was not clear to me.
Eventually I did figure it out and was able to wire some flashing LEDs to switch #3, which was the lowest amperage out of the 4. I don't believe that all 4 switches have the same amp rating.
If you look up under the dash, above the pedals you can find the wires for each switch. I don't remember exactly, but it almost seems that they were numbered or otherwise marked for which switch the wires went to. I don't feel like laying on my back on the truck floor and looking up in there with a flash light at this time.

 

here you go..

select electrical wiring.. and it will download wiring... go to uplifter area

https://www.fleet.ford.com/truckbbas...6/maintoc.html

 

It would of been so much easier if the Pass-Threw wires used the same color code as the
Up-Fitter Switches.
I couldn't find on (any) wiring schematic (anywhere) that said to choose (any) of the (4)
Pass-Threw wires and connect it to the Colored Up-Fitter of your Amperage Choice. Then choose that same colored Pass-Threw wire in the Engine Compartment to complete your Accessory wiring connection.
Up-Fitter Switches simplified.

 

It's more flexible the way it is.

 

<hijack>
Do trucks that did not come with up-fitter switches still have the pass-through wires?
</hijack>

 

Yes, they do come with them.