Let me give a little background on this. Order a new interior gadget that has to be powered. We have all done it, have lots of things on the inside of the car and having to steal power from various sources. Its a pain in the ass to say the least. Here is what I do, and I think if you take the time to do it just once you will NEVER do it any other way. Plus if you EVER add anything else, and lets be honest you will, you will NEVER have to spend any time wiring up the new toy. Thats one of the best parts about this, is the time you save from here on out.
I run all my "add ons" with a relay. Its super safe, reliable and quick.
Terminal strip from radio shack
add-a-fuse from parts store
30-40 amp relay from parts store(or radio shack if they have 12v one)
some wire(I do 10gauge for battery power to relay, 14 gauge for switched 12v source, 10 gauge for ground and 12 gauge for jumpers on terminal strip)
A bit overkill, but it works like a charm. This will allow the use of MANY things you want to "turn on" when the key is cycled forward.
All you do is wire a relay up normally(not hard, most come with the pin-out for the 4 pins). Run one wire strait from your battery to your constant 12v pin(pin 30 ). You remove a 5 amp fuse from fusebox, place the add-a-fuse in its spot then you put the 5 amp fuse in the extra slot, you run that wire to the switched 12v pin( pin 86).
You run the ground to pin 85. You run a wire from pin 87 to the terminal strip. You jump one side of the terminal strip from one slot to the next, then that slot to the next, and so on until your number of desired "outputs" are completed(this realy sounds more difficult than it is)
All the relay does is allow you to run something that requres a heavy load(bunch of gauges, wideband, etc..) All it does is you have constant 12v coming into it with big wire. The small wire acts as a signal to close the circut sending that constant 12v to all your gauges, wideband, etc..
You can do it yourself, even if youve never done it before in about 30 mins tops. And trust me when I say you will be SO glad you did it this way. Its a great feeling to get something in the mail and NOT have to do all the "normal" wiring that comes along iwth it. You can complete the wiring in under a minuite for all your new gadgets using this method and honestly it takes just a few minuites longer to go ahead and do it this way from the start. After you do it like this ONCE you will allways do it.
I will add pictures as soon as I have some time. I came up with this quite a few years back. I am sure by now(or possibly before) someone else also came up with this idea, Im not vain enough to think Im the only one that thought of this, and to them I also say kudo's!
Here it is. I tried taking pictures of my setup in the car but I realized it would be more confusing than just drawing a picture. If anyone has any questions let me know and Ill add more too it.