I just replaced a set of off road lights on my safari rack. Problem is that my mini-mag puts out more light than they do. I'm sure its a wiring issue. Any ideas? it came with a prebuilt plug and play harness.

 

It would help if you said what the total wattage is per circuit, what size wire you used and the distance between the relay and the lights. You have to know the 1st and 3rd to properly size the 2nd.
Oh, also the size of the main feed wire to the relay and the size of that wire as well.

 

And if the wiring set up uses truck and roof rack metal as the ground return, rather than a separate ground wire, you could have a seies of poor metal to metal connections that are causing too much voltage drop, when compared to a stout, clean, properly terminated cable.

 

It's running to a set of 55 watt lights mounted to my roof rack, so totally 8-12 feet. Also I'm using 10 gauge wire on the main feed into 12-14 gauge.
I'm thinking it's the ground though since the factory ground is real real flimsy.

 

you must have a set of jumper cables run the jumper cables from your roof rack to the negitive battery post, if that doesnt change it it's not your ground. If it does you need to run yourself a new ground or drive around with jumper cables on your rack.

 

Did you wire to a new switch and then thru a relay, to power the lights, if not that can be your problem.

 

Well, that's sort of vague. But assuming the relay is 2 feet from the battery and then you have 12 or 14 gauge(it makes a difference which it is) the remaining 10 feet you'll have a volt drop of either .17v or .26v, either of which is fine.
Yes, that would leave the ground, assuming the positive connections are all solid. If you're trying to ground to the rack it's not going to be a good ground.

 

I used a new premade wiring harness with all the fuses and 12v resistor. This afternoon I did a variation of the jumper cable idea. I ran two wires from one lamp to the passenger side fog lamp harness (no fog light hooked up ). Then I turned on both lights., and viola! They have the same brightness. so I have identical lights on two separate harnesses that appear to cast identical beams. Only two options left. Take it all back off, return the cheap Pilot lights back to the store and buy more expensive lights. Or just leave them on and put some decent bulbs in them. Maybe some PIAA 55 = 100 xtreme white. About the same money but one way does not involve taking it ask off and putting new stuff on .
I also have a set if KC 57's.that im thinking of mounting on the sides for alley lights

 

Why did you install a resistor in the circuit? A resistor is used to reduce the voltage, like for a fan, so the fan runs slower.

 

got it working right. just by accident I unplugged one light and noticed the other get brighter. so I ran separate grounds for each and viola!