I drew out a schematic on how I will be wiring them (power, ground, and illumination only, no load or sending units drawn here), and I just wanted to run it by you all first to make sure that I am doing everything right. Here is the goal.
I want to install up to six gauges and six switches for now. I want the gauges and switches to illuminate only when the lights are turned on (i.e. instrument cluster illuminates), and want the switches to be powered only when the truck is turned on. The main goal is to make sure that the install is not only neat and clean, bu also safe. So what do you all think? Also, is there a limit to the number of things I can run off the positive circuit (gauges and switches) safely? I just do not want to overload things. Will I be okay with a 20A fuse on the circuits?

 

Also, where do I need to tap into for the switched hot and the illumination? Anybody know the wire colors on a 2003 F-350 PSD 6.0L? Thanks!

 

While your schematic looks good, your making it WAY more complicated then it needs to be. Also, why would you want a switch to turn the illumination off? If you crunch some numbers with Ohms law you will find that you could tie many of the circuits together instead of running a dedicated circuit for each gauge.

 

Good point about the switched (relay) illumination, and you are right. I will probably just take out the #1 relay and run it straight into the terminal strip. I don't think I would ever turn the gauges on without the truck running, but if I do I would like them to illuminate with the factory units. Thanks for the tip!

As for the complexity of the circuits, the main thing was to make sure everything was as safe as possible. I did not want to keep splicing into wire after wire after wire, therefore I decided to run terminal strips instead. Just a little cleaner, a little safer.

 

Here is a more revised version.
Anything you would change? How could I make it less complicated?

 

Actually, I was looking at the first schematic, and it should come on any time the lights are turned on, correct?

 

I just want to make sure I have enough current to feed all the lighting in the switches and gauges, but do not overload anything and start a fire.

 

Just noticed, but were you referring to the relay or the switches in regards to the illumination? The way I was running it, the hot will go into the relay, which is switched on by the illumination (dimmer wire). This was to allow enough amperage to the gauges for illumination. There were actually 12 illumination wires coming off that circuit, six provide hot to the gauges, six provide illumination to the switches.

 

I think the way you have the left-most relay wired up, you'll either have the illumination off, or on full brightness. If you would get behind the headlight switch and tap into the Light Blue/Red wire then you can dim the illumination of the gauges & switches, the same as you do your instrument cluster/radio/etc. I would probably get rid of the left-most relay and connect the Light Blue/Red wire directly to your terminal strip.
EDIT --- slow typing syndrome... I see you did this in your next revision.

For the gauges and switches that are mounted together, I would combine the illumination, powers, and grounds. Like, for my quad pillar gauges, they all share a +12V, GND, and ILLUM. You can see that in my schematic here:
http://www.frontiernet.net/~slray/04...eSchematic.jpg

However, if you do run a separate set of wires to each gauge, a slick way to do it is to get the length of wires and hook one end of them into a vise. Then chuck the other end of these wires into a drill. Then just run the drill to create a really nice, consistent, twisted set of wires. That'll help keep everything neat.

You might want to go smaller on the fuse to the gauges. You could end up with some problem that won't blow a 20A fuse, but could still damage the gauges. I use a 1A fuse in my quad gauges.

There's a hot-in-accessory customer use wire behind the dash, kind of behind the cubby hole. I don't remember what color it is but you'll find it folded back to the harness. Possibly with a heat shrink jimmy hat on it.

 

The illumination circuit can handle quite few additional things. I have four gauges, 4 Carling switches, and my rear wiper switch so that's 9 things off the top of my head.

 

Actually Jason, I came up with the idea to use terminal strips off your project, thanks for that idea. Sorry, I just noticed I forgot to mention that.

I thought of running splice into splice for the gauges, this is how i did it on several of my Mustangs, but they were all two gauges. I am running four gauges up top in an overhead pod and don't want to overload anything. I just don't want an electrical fire, especially when the wires under the headliner.
If I do run a hot to the switches for illumination off of the terminal strip, would I have enough amperage loss to cause illumination issues?

 

Same here... I will be running 12 for starters, six gauges, six switches.

 

Think 1A is enough? I would think at least 15A for the gauges.

 

No problem!

I guess it depends on how much current the illumination bulbs draw, but I wouldn't think you would have any problems. Are you concerned that running the illumination for four gauges on a single wire will cause problems? I would think if you use 14 or 16AWG you would be totally safe in that regard. I believe 16AWG is good for 20A at 12V and 14AWG would be even more.

I don't know much about gauges other than the Phantoms I run but I believe gauges typically don't draw much current. 1A for four gauges works for me. Which gauges do you plan to run?

 

Wanting to run DiPricol gauges which have LEDs I believe. I have the pyro and the boost gauge is coming in this week.