Aux Lighting and Negative Switching Advice

[RayNAz]

I'm planning on adding some auxiliary lighting to my 98 & 1/2 2500 and while poking around under the hood I noticed that the existing fog lights (and presumably other lights) appear to use negative switching.  For those who've been down this path before, do you think I should use negative switching for any new lighting or other accessories so that it's all the same?  If so should I do this for the switches in the cab as well or just use positive switching at that point and use the relays under the hood to switch ground?  I can do it either way but I have to admit that positive switching feels more natural to me.  I'm just curious if either approach is likely to bite me in the butt later for some reason I haven't thought of.

[Andyba20]

The 98.5’s are often an oddball mismatch of some parts/designs leftover from the early 98’s…by that I mean I’m not sure which fog light switch you got, but I’d say do whatever you’re most comfortable with. Honestly once you get over about 5 or 6 accessories the wiring starts to get hard to keep organized. Lots of wires, relays, fuses-and not just in the engine bay, but in the cab too. The solid state switch panels are starting to look really good to me. 
 

This for example would be the budget option-made in China

https://a.co/d/6I76ama
 

 

or you can go premium and American made with these guys

 

https://www.switchpros.com

 

 

[Tractorman]

On 5/17/2024 at 6:35 PM, RayNAz said:

For those who've been down this path before, do you think I should use negative switching for any new lighting or other accessories so that it's all the same?

 

One good reason to stay with the negative switching with headlights and fog lights is because the batteries and lights are in the same compartment - under the hood.  This  makes it easy to run a short hot fused wire directly to the the headlights or fog lights. 

 

Then the very long and circuitous route for the ground wire from the lights into the cab, through the various control switches, and then eventually to a ground makes it impossible to blow a fuse if a wire is unintentionally grounded after leaving the headlight or fog light.  It reduces the ingredients for a possible fire.

 

But, in the end, either way will work fine.

 

- John

[Mopar1973Man]

Keep in mind that like the headlights you can blow a fuse and get back feed and still have a lit bulb. 

[QuadRunnerJake]

Im not sure how far along in the project you are but I successfully changed my negative switched 3 wire headlights. I recommend grabbing a fuse and relay box from Amazon cheap. I grabbed one that holds 6 relays and 6 fuses and wired it myself. you can buy them pre wired as well with just a loom sticking out the end for simplicity.

 

I installed BiLED NHK projectors which have 4 wires, pos/neg and 2 nonpolar for the hibeam solenoid. I used cut up headlight bulbs as the adapters and soldered wire to the leads then filled with hot glue for insulation. I was able to use one relay per headlight operating both high and low beam functions. For the wiring I used 2 forward bias shottky diodes per headlight to address backfeeding.

 

The bileds I used cost about 120. The housings cost me 100, wire and diodes another $30 or so. They pull around 10 amps each and have a great cutoff line. Definitely removed a ton of load on the electrical system.

[Royal Squire]

Can you share any photos?