I bought a used nitrous kit and it is the first time I have messed with nitrous. My fuel solenoid wires are both red and my N2o solenoid wires are both black. I was told it does not matter which one you hook to power or ground on either one of them. I was also told to run my grounds through my switch, not my power, is this right. Thanks

 

It doesn't matter which is positive or negative. Since it is a solenoid the plus and minus together wrapped like a coil will create a magnetic field. This in turn opens the solenoid to allow nitrous or fuel to pass through it. I have always ran power through the switches but either will work.

 

http://www.holley.com/data/Products/...A5060-SNOS.pdf

I wired mine using the diagram on page 12 above, works good.

Make sure you use a nitrous filter before the solenoid.

 

It doesn’t matter which wire you use for the ground and the + and it doesn’t matter which one you switch either.

Some people prefer to switch the ground since it means that you only have to run one wire into the passenger compartment (you can just run the other side of the switch to any ground inside the passenger compartment), some prefer switching the hot lead for safety (if something happens to the insulation and the switched lead shorts out/grounds it will just burn out the fuse, you are fusing your circuit, right? If you’re switching your ground if the same thing happens it will activate the N2O system).

I usually just switch the ground, but I'll usually run a relay also.