what wires go where?

Im working on a project for my car. I am adding leads from my battery, to under my head unit. I am hard wiring my gps, radar detector, and fog lights. I bought a project enclosure from radioshack, and 3 spst rocker switches. I wired them in parallel( I think, i just brought both the pos and neg to distribution strips, and added the switches on the line. On my Bench, using one of those battery powered jumpers so you can jump your car without another car. The jumper was giving me 12.91v, both going in and measuring out of each switch output. But when i went and hooked it up in the car, only the radar detector come on. The radar detector is only using 1.5a, so im guessing the others are no coming on because there isn't enough juice.

Can anyone tell me how to wire this in series?, or anything that will make it work? i haven't messed with electronics before so i don't fully know how to problem solve. I don't have any resistors, relays, etc wired in. its just the fuse, switch, and the component.
Do i need to add a resistor or capacitor or relay or something?

Thanks so much,
Ben

Couple questions:

1- model of GPS?
2- model of detector?
3- watt-rating of fog lights?
4- what gauge wire are you using to supply the distribution strips (both pos and neg)
5- where are you sourcing the voltage from? Under dash? Battery? Be specific.
6- where are you sourcing ground?
7- are the fog lights grounded? Where? Bolted to clean metal, or into a factory bolt, or some other?
8- The lights, specifically, ought to be controlled via relay.
9- gauge of wire to each load?


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"Always listen to experts. They'll tell you what can't be done, and why. Then do it. - Robert A. Heinlein"