David, from my installation of the current relay harness, and perhaps because of the Boss plow harness (which is plug-n-play), I ran across a wire to each truck headlight that actually reversed its polarity when switching between high and low beams, and I'm thinking it was the reason the highbeams improved and the lows did not. It just seems wrong.
Each headlight should have + to each filament and a common ground. Three wires to each plug and they should not change polarity. On or Off. Positive or negative. Period. At least that is my opinion. So I fall into that "Not sure if I have positive or negative switched" category Daniel Sterns speaks of in the last sentence of the quote below. The other possibility (probability) is I just have a screwed-up and incompatible set of harnesses and switches.
Like I said, Boss stopped issuing harnesses like mine and began including harnesses with relays for these Dodges shortly after I bought my plow. The jerks KNOW they were having and/or causing problems with the original no-relay harnesses but would NOT upgrade mine despite all the problems I was having. They want some outrageous amount of money for a new, updated harness ($300+ IIRC). Given that type of "up yours" customer service on such an expensive purchase and dangerous problem, I won't give those jerks another dime for anything!
New, separate harnesses that are actually compatible and use relays for all the headlights are what's needed.
The Boss plow headlight assemblies do have their own combination parking lights/turn signals, too. They and the truck park lights and turn signals always work at the same time when the plow is mounted, unlike the headlights. they have never been a problem, though I would also like to wire all of my parking and roof lights through a relay to alleviate the load on my headlight switch. LED's would do the same thing, but cost a lot more.
Here is where Sterns addresses the best way to wire a vehicle which either does or may have switched negative leads:
from Daniel Sterns:
SPECIAL CONSIDERATIONS FOR GROUND-SWITCHED SYSTEMS
Many Japanese vehicles, as well as a few others, use a "ground-switched" headlamp circuit. In these circuits, the headlamp and beam selector switch break or complete the ground side of the headlamp circuit, rather than the feed side. On these systems, it's imperative to use both negative and positive existing headlamp wires to trigger the relays. It is tempting to run the existing headlamp feed wire to relay terminal 86 (trigger feed) and simply find a convenient ground for relay terminal 85 (trigger ground). However, this will not work with ground-switched systems. Run the vehicle's existing feed wire to terminal 86, and run the vehicle's existing ground wire to terminal85.
Now, what are we going to do now that we've used-up our one and only ground wire on the 85 terminal of the low beam relay, but we still have to install the high beam relay? Go to the other side of the car and you have another ground wire! Remember, the relay trigger circuits can be as long as you like, because they take insignificant power. So, you can extend the vehicle's existing headlamp wires to your relay mounting location. It is fine to use this method regardless of whether you have a ground-switched system or not, so go ahead and use it if you're not sure.
This is a "you cannot go wrong" method of wiring the relays, no matter which polarity is switched. Not a bad idea. All bases are covered.
The Boss plow harness:
It installs by unplugging the sockets from both (single bulb/standard) truck headlights and plugging them into the Boss harness. It then has its own headlight sockets that plug onto the truck headlights.
The truck's factory headlight switch works the same as before, turning both the parking lights and the headlights on or off.
The truck's dimmer switch aslo functions as before and controls the hi/lo beams of whichever set of headlights you have selected with the toggle switch.
TOGGLE SWITCH: With the Boss harness installed, there is now a toggle switch with 6 wires from that Boss harness (which is plugged into the factory harness at the headlights) that also mounts in the cab. It is two position (double-pole/double-throw) and selects entirely between truck headlights OR plow headlights. You cannot have both on at once, nor do you need both at once.
If you remove the quick-disconnect plow, the plow headlights go with it. If you forget to move the toggle switch back to "truck headlights" position, you simply will not have any headlights.
So the Boss harness is not stand-alone. It incorporates itself into the Dodge truck harness at the headlight sockets and uses the same, already-overloaded, Dodge headlight switch and dimmer switch. It simply adds another toggle switch, several connectors, and many, many extra feet of wire. No relays at all.
It simply intercepts the juice from the trucks's headlight/dimmer switches and wiring right at the headlights themselves. The harness then sends that juice to a toggle switch in the cab which, in turn, diverts it either right back to the truck headlights or over to the plow headlights.
You can see where all that extra wire and connections will put an even greater burden upon the factory's already-weak design. The toggle switch gets very hot from carrying all of the juice for whichever set of headlights it is diverting the power to, just like the factory headlight switch does.
The design is not totally bad, it just needs relays to alleviate the need to carry all of the headlight juice through all those connectors, wiring, and that toggle switch.
What I have in mind:
If you could intercept the 2 (high and low beam) wires that come out of the truck's dimmer switch and go to the headlights and divert them through that same double-pole/double-throw toggle switch (which would turn the two wires into four wires to enable selection of either set of headlights), then down to four RELAYS (2 for the plow lights and 2 for the truck lights), you could simplify the entire harness AND completely take the load off all the wiring, switches, and connectors. The toggle would still let you select which set of headlights get the juice.
Wire those trigger wires, and the ground wires, to the relays like Daniel Sterns says. Use the relays' output leads to power the bulb filaments the way you said. Problems solved.
Note: This is if ONE relay can power all four filaments of the Sportlights on Highbeam, and if will one relay can power both filaments for lowbeam. If not, then the Sportlights would simply need two additional relays. The daniel sterns website seems to indicate that 2 relays are more than enough to power a set of Sportlights. SUVLights uses four.
After winter is over, I find I can increase my truck headlight brightness significantly by completely unplugging the Boss harness at the headlight sockets and plugging the truck's headlight sockets back into the headlights. But, though improved noticeably, they still suck.
Attention: TDR Forum Junkies 
