Spare power switch/connector

[Golfnut]

I've looked at that manual several times and see exactly what you are referring to. The "spare circuits" connector they are referring to will not work for what I want. I need a switched circuit for a dump valve I want to put on my trailer. The truck has two switches that have power to them (and through them back into a bigger bundle of wires) and supposedly there are terminals in the engine compartment or under the cab I can plug into. I cannot find any such terminals.