How To Easily Assemble A Removable LED Light Bar For Your Truck Or Car’s Roof

Okay, I’m the proud new owner of a 2021 Ram 2500 Tradesman and the original halogen lights were pretty anemic. I did two things to address this – first, I replaced the high beams with Lasfit LED emitters and that’s a story for another day. With that said though, I’ll tell you that upgrading to the Lasfit LED high beams was stunningly worth it – I can’t tell you the last time I was so happy with an upgrade.

Now that I am done gushing over the high beam upgrade, the second thing I did was to investigate installing a LED light bar on the truck. That’s really the focus of this post.

I guess it must be the pandemic because there aren’t a lot of custom fit aftermarket options right now but there are still a ton of lighting options using general fit LED light bars – the kind that you normally bolt on to a bumper, roll bar, etc.

My first thought was to mount a light on the bumper but I run a Western plow in the winter. I could have mounted a 26″ bar behind the front lower plastic grill in the bumper or even cut it out for a clear shot but it wasn’t really appealing to me.

Then I got to thinking about how tall the truck was. My 2021 Ram 2500 with the snow package is sitting pretty tall in the air. The top of the cab is about six and a half feet (80-ish inches) off the ground. If I mounted a light bar up there, it would have the elevation to cast a ton of light.

Lighting Options

Over the years, I’ve used a number of inexpensive light bars off Amazon and had while some brands weren’t so great due to leaking water into the LEDs, I’ve had pretty good luck with Nilight. You’ll read mixed reviews of their customer service but fortunately I’ve not needed to work with them.

So, I started looking at NiLights and was particularly interested in their triple row light bars as they can output a ton of light. Honestly, for any of these vendors, take their lumen and wattage claims with a huge grain of salt – there’s a ton of marketing hype. In general, bigger bars and more emitters give you more light – that’s just a rule of thumb to go by.

So, I’ve had light bars up to 12″ wide in the past but they were double row and nothing to spectacular in terms of light output. So, I figured I wanted another Nilight and some width greater than 20″ and they have a bunch of options.

In terms of mounting, I really didn’t want to go drilling into my new truck. On one hand I could mount a light behind the plastic lower grill in the bumper but I really wanted to go high because I do plan to install LED fog lights in the future.

Magnetic Mounts

So, one way to mount is to use rubber coated magnetic mounts. They are removable and hold pretty good but they honestly do have limits and will blow off the truck if you don’t think things through carefully. I really wanted to go this route, at least for now.

Going with magnetic mounts does require you to think about some things. First and foremost, are they strong enough to hold the light in position? What you will find is that they tend to be very strong and pulling a magnet straight off a good metal roof is genuinely hard but that’s not the real issue. You need them to not gradually slide backward and come off at the speeds you plan. In general, the bigger the surface area of the light (width x height).

As I thought about it, I reigned in my length to 26″. I sure debated the 37″ bar but there were two reasons why I went with the shorter bar. First, guys reported that the actual draw of the 26″ Nilight 18025C-A light bar was around 5 amps and that was good because I planned to power the light from the dash mounted cigarette lighter – more on that shortly.

Second, I wanted to lower the risk of the light sliding around. The 26″ Nilight 18025C-A bar comes with three mounting points but I wanted to add more to make sure it didn’t move so I ordered additional set of the Nilight 90035B mounting brackets. That then gave me the ability to mount five of the magnetic bases. I figured that would do the job.

Powering the Nilight 18025C-A Bar

With all of the lighting gear on order, the next thing to consider was the power. Since it was going to be removable, I wanted the power to be mobile as well and not hardwired.

For those of us old enough to remember the old cigarette lighters you know where the name comes from. For those of you wondering what I am talking about, I am talking about the odd looking tubular 12 volt power receptacle in your car or truck. Back in the day, there was a little plug that you pushed in that would cause a little heating element to get red hot and you could light a cigarette or stogie from it … or anything else for that matter – it was like a little red hot space heater or stove element.

In most vehicles, the units can provide 15-20 amps. In a Ram, my understanding is that the center dash unit has a 20 amp fuse. If you are trying to calculate watts, volts x amps = watts so a 20 amp 12 volt circuit can provide 240 watts.

Remember my earlier comment about light bar watt and lumen claims typically being higher than reality? The 26″ bar listing says 540 watts. That is a ton of juice — maybe it’s what it would be if some old incandescent bulb was used but it’s not really drawing that.

There are these really cool switched plugs that have a on/off switch along with a momentary switch and a 10 foot cord. They are well made but I do wish the wire was thicker but it didn’t cause a problem. Note, you can buy these with either the ground (negative) or positive being the momentary switched circuit. I opted for the positive momentary switch because I could just turn the light on for second, let go and it would shut off. If you don’t want it at all, you can just cut off blue momentary wire.

Adding The Mounts To The Nilight 18025C-A

I should point out that I did try just using the original three mounting points that came with the bar and three magnets. During some highway driving tests during the rain I thought it moved some and didn’t think that was secure enough, at least not to my liking. The lights are modular so adding a couple more mounts was easily done.

The first thing I did was to unscrew the end cap from the end without the wire. I removed the end cap and the gasket so I could then slide in two extra M8 hex nut for the two extra mounts I planned.

I removed the cap from the end with no wire, moved the gasket out the way, and slid in two new M8 nuts. I was then careful to make sure the gasket was positioned correctly when I inserted and started the little bolts by hand before using my power screw driver to run them down snug.

In terms of the mounts, I found that their supplied allen/hex socket screws were really a bad idea on their part. You can’t access them easily at all and they limit adjustments so I switched to regular hex head M8 bolts.

With an M8 bolt in place, you can turn the rubberized magnetic mounting disc and tighten or loosen it accordingly. I replaced all of the little hex head socket bolts with hex heads as shown above. I took the little hex socket bolt into my local Ace Hardware and found replacements of the same length.
As with the bolts on the rubber mounts, I replaced the hex sockets on the body too. I honestly have no idea why they opted for sockets vs. head head bolts. The hex heads allow for more rotation and easy access with an open end wrench.

I did apply blue Loc-tite to the bolts going into the rubber pads. In hindsight, I think this might have been overkill. If I ever want to take the pads off, it will take a bit more effort but then again they aren’t going to vibrate loose so easily either.

To make the spacing symmetrical I just moved in X screw heads from each end, centered the mounting block and tightened it down. In my case, I wanted the light to point straight head so I did have to play with that a bit and then match all of the mounts to the same angle.
Here’s the rear view. Once I figured out the position for the light to be straight ahead, I approximated the angle on the others by paying attention to the location of the top of the mount relative to the cooling fin.

Wiring The Nilight 18025C-A

Wiring is very straight forward – red line in the light’s short lead cord to the red line on the power cord. If you want the momentary positive to trip the light also, connect the blue and red cord together. Only do this if you buy the momentary positive version of the cord.

Here’s the switch assembly and it’s cord with the black cord from the light swooping in from the top left. The small black tool is used to trim back the protective outer
case on cable assemblies so you can then get to the exposed individual wires. They are cheap and very handy. The alternative is careful slitting with a box cutter/razor.
Red to Red, Black to Black and combine the blue momentary positive to the red positive on the power cord – I just twisted them together and then soldered. Only do this if you made sure to buy the momentary switched positive version of the switch. If you mistakenly bought the negative momentary version you will pop the fuse in the nose of the switch housing because that will be a dead short. That fuse is replaceable by the way.

As far as wiring goes, you can use any of the solderless crimp on connectors or you can just solder the lines together. If I know I will need to take something apart then I will use good crimp on fittings. Otherwise, if I want a slim connection that will last, I use a soldering iron and resin flux core solder.

Be sure to test everything before you close up the circuits. I tested the LED light bar itself before I did anything else.

After soldering, I like to put shrink tubes over each line and then over the bundle to keep moisture out and reduce strain. By the way, if you aren’t familiar with shrink tubing, it shrinks when heated – I prefer to use a heat gun but have also used a lighter in a pinch.

If I want to reinforce it further then I may add on a layer or two of quality 3M electrical tape – overkill I know but I don’t want things to fail easily from flexing or moisture.

Shrink tubing assortment sets are very handy to have around.

I also looked at where the light cord was going to rub on my truck’s roof and added a piece of thick decal vinyl to protect the paint.

So the plug and switches work quite well being in the center dash plug like this. Very easy to reach and turn on or off. When on, the little red LED lights up so you do have an in-cab reminder that the bar is on (trust me, at night, you’ll know it’s on).
You can see how I have the cord run. Again, this is meant to be removable and something I can move around as needed. So yeah. there is a loose cord but it is manageable.
So the light us up top and I run the wire in actually just behind the pillar between the driver and passenger doors in the crew cab. I then run the wire behind the driver’s headrest and down along the center console. Note, there is thick vinyl decal paint protector where the line touches the pain – and about two inches on either side just to play it safe.
So the cord runs under the driver side headrest and then up and out the passenger rear door in the crew cab. I wish there was another 2-3 feet of cord so I could have run it to the floor and around the bottom of my chair but you know, it works. I could have spliced in more wire with pros and cons but I decided to keep it simple.
It really clamps down well on the flat portion of the roof but not in the back with the reinforcing bends. I center the light by eyeball aligning the center mount of the bar with the center roof marker light. The actual bottom of the light bar (not the mounts) is about 81-ish” off the ground. Also, you can’t see it but as mentioned, there is thick 3M Vivid vinyl decal material under the cord.
It’s hard to get the 3M Vivid tape to show up unless you get the angle just right to see the edges. There are two pieces here – one wrapping over the edge of the roof and a second wider piece to protect the paint if the cord is blowing around in the wind much.

Nilight 18025C-A Results

Let’s look at some photos that I took at night and the measures at all based on my laser range finder that I measured before hand from the front of the truck:

These are the stock OEM low beams. Notice how they really limit upward light. The bright oak tree trunk you see slightly left of center is at 23 yards. If you can see the silver tarp in the background, that is at 47 yards.
Ok, mow this one is with the Lasfit LED high beams turned on. The leaf pile in the woods is at 57 yards.
Alright, this is with the low, high and LED light bar running. The light output is amazing. You can’t see it in the photo obviously but the light bar was lighting up a ton of stuff to the left and right as well. The next big tree in the left of the photo is at 31 yards and the swing set is at 44 yards. There’s just a ton of light. This is exactly what I wanted – the Nilight LED bar I bought has a mix of flood and spot emitters to generate this much light.
Low beam only from about 7 yards.
Low and High beam lights at 7 yards. The big shadow is the top left light of my plow.
Low, High and Light Bar at 7 yards.

Summary

First off, it is stunningly bright and casts it very well both forward and to the sides – the breadth of the field of light cast actually surprised me. So, in terms of the shear volume of light it is kicking out and it’s ability to light things up in all directions, it definitely exceeded my expectations.

The switch works remarkably well. The switches have a nice feel and I like that there is a fuse in the switch assembly protecting the truck’s outlet. At no time did the cord feel warm due to excessive draw and I can’t see that it is limiting the brightness of the LEDs any so that worked out just fine.

Next, it seems to stay put – even during rain. Most of my driving has been around town and 35-45mph. I did go on the highway at 65-75mph for 10-15 minutes a few times but not for hours on end. I also have no intention of putting this through a car wash – I really am not sure how it would fare one way or the other.

I would recommend that you keep a towel in your truck to clean the roof before you clamp on the light and also inspect the magnets to make sure they are clear — otherwise you are liable to scratch up the roof or where ever you clamp the light to.

I also decided to keep the light stored in an old duffel bag under my back seat vs. having any risk of it coming off. I put a micro fiber towel in there too – I mainly bagged it to prevent stuff from getting stuck to the magnets and then scratching things up.

This is the light bar, duffel bag and towel that I stash under the rear seat.

The only downside is that I would need to know before hand that I might need the light and install it vs. leaving it attached all the time. I figure in the Spring that I’ll look into installing the flood lights and then decide if I want to do anything after that.

Last photo for now 🙂

So, I am very happy with the result and hope this gives you some ideas as well.


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