If I add clearance lights, aux. backup lights, fog lights, side markers, KC highlighters, etc... Should they all be on relays? What about the tail lights, anybody using relays for those? Where would I start to plan the wiring/relay system, ( ie. how many relays per light group, wire gauge, relay size?)

 

I'd say go with a relay for the KC's for sure, and it wouldn't hurt for anything else. Basically you need to run two separate circuits through each relay, one is the power circuit for what ever you are running, and the other is the circuit connected to a switched source (ignition or separate switch.) The switched source doesn't need to be very heavy, I'd use 16 or 18 AWG. The power circuit should be heavy enough to carry the current to what you are running. I'd run at least 12 AWG to the off road lights. You will need a relay for each group of lights you hook up, unless you want to get real complex. I'd suggest mounting the relay inline with the shortest path of the power circuit, that way you don't have to run the more expensive heavy wire through the cab. I could go on, but I feel like I'm rambling. An specific questions, just ask.

 

I have my headlights and my 55 watt backup lights on relays.

If I was to add more clearance lights, I'd put that circuit on a relay.

I wouldn't bother relaying the tail lights. If you tow, put your trailer harness on relays.

 

Since my trailer harness is fed off the factory tail light/clearance light wiring, couldnt I put the entire circuit on a relay, and by doing so, have the trailer running lights on the same relay??
My thought is that I could insert a relay into the wiring coming off teh headlight switch taht feeds the running and clearance lights, if Icould figure out which one it is...

 

Sure could.

The reason I suggested putting the trailer harness on relays is that if you have a properly wired 7 pole, you have a high capacity B+ wire back there already so there is minimal wiring involved.

 

YES and maybe.

You can use either strong relays, or BIG wire and BIG stout toggle-switches.

A relay is simply a switch, either magnetic or thermal, that "MAKES" the circuit, just like a switch would.

I have went both ways, depending on what I am hooking up.

I prefer a BIG STOUT toggle-switch, over using a relay, as the switch is much more positive and far easier to trouble-shoot or completely by-pass on the side of a busy interstate.

The advantage of a relay is that it can re-route the heavy current that would otherwise be passing through a questionable light-duty switch, requiring the switch to only carry the minimal current necessary to trigger the relay.

A good toggle-switch will sound like the hammer on a 45 being cocked "SNAPPP!!!!", not some wimpy little "click".