Sunday, September 27, 2020

How To Install an Overhead Dome Light

C3 Corvette coupe interiors are dark, and in order to solve that issue—to a certain degree—Chevy engineers finally added a much-needed overhead dome light starting with 1977 models.

That, of course, leaves 1968-1976 coupes in the dark (no pun intended).


So I had to do something about it, and my solution was to repurpose the original storage compartment dome light fixture, which I deleted in favor of LED string lights.

Using the OEM dome light looked period-correct and almost identical to 1977-on models. I say "almost-identical" since the factory recessed the dome light base about a 1/4 of an inch, and I did not want or need to emulate the factory look to that degree.

Needless to say, adding a dome light necessitates cutting a hole in the T-bar trim, as well as fabrication of a wiring harness that would be spliced into the existing courtesy lights harness in order for the dome light to turn on and off by opening and closing the doors.

Since I did not have exact measurements as to where the factory placed the overhead dome light in 1977-1982 Corvettes, I positioned mine based on what made sense to me as I sat in the driver's seat. This means that the rear edge of the base is 15¼ inches from the rear edge of the T-bar trim piece.

With the overhead dome light position figured out, I started removing interior trim panels in order to get the T-bar trim panel out of the car. Yes, many panels have to be removed to get this job done.

Of course, the T-tops have to be removed, followed by the sun visors.


Next, you have to remove the windshield crossbar trim piece.


The two halo panels above the seats must also come off. Take your time to remove each panel and keep track of all the hardware to ease installation.


At this point, the T-bar trim panel can be removed. But that can be tricky as well as nerve-wracking since it is held in position by three "friction" threaded studs. The only way to remove the panel is to carefully pull down near the location of the three studs in order to loosen it.

And keep in mind that—in most cases—these are 40-plus-year-old parts that can be damaged or broken when they are manhandled, so take your time. 


The three red arrows below show the location of the threaded studs.


In turn, the studs (close-up below), push into three holes with stainless steel retainers as shown in the second photo below.



Next, I used an existing hole on the inside of the trim panel that lined up almost perfectly with the center of the dome light location I had chosen. I drilled a 1/4" hole to mark the exact spot and use it as a reference.



With the exact center of the dome light assembly established, I turned my attention to the wiring harness. This is a very simple harness since all that's required are two wires to power the light and splice into the factory harness.

I measured a generous approximate length of wire that would be required and went to work.

As the photo below shows, I had to use wiring I had handy, but that was of no consequence since I spliced each end of the harness with the correct colored wires. I also used Solder Seal connectors to have a good connection.

You may want to watch the short video at the end of this article to see how they are soldered in place with a heat gun.


And in order to avoid confusion with different wire colors, and for a factory-look, once all the ends were spliced together I used black cloth wiring harness tape.


I also measured and made another wiring harness that ran from the sail panel all the way to the LHS end of the storage compartment. This harness was spliced into the existing factory orange and white dome light wiring.

With the wiring harness done, I turned my attention to the dome light assembly itself. Installation would require cutting an opening into the T-bar trim panel. I used the hole I had drilled earlier to run the wire and position the fixture.



One of my concerns was not having enough room between the dome light assembly and the T-bar itself, especially since there would be electrical wiring in such close proximity.

In order to ensure there would be enough room as well as clearance, I used the depth gauge of my calipers to measure.



This proved that there would be at least a 1/4" clearance between the light fixture and the T-bar.


With that assurance, I started measuring and marking where I would need to cut. I started by turning the light assembly base upside down and eyeballing its position.


I carefully measured and used masking tape to define the overall area.


I then measured some more and marked the area that would allow the protrusion of the base to sit inside the panel. This portion of the base holds the light bulb as well as the wire connectors.


I then drilled four 1/4" holes in each corner. Doing so made cutting the panel a lot safer and easier.


I used a small ruler to ensure straight cuts. A utility knife with a sharp blade cut through the vinyl, foam, and cardboard backing easily. The vinyl was extremely brittle after more than four decades.


With the opening made, I fitted the base in order to mark the exact location of the screw holes.


I then used an awl to mark the screw locations. To make my life easier, I decided to use two sheet metal screws to secure the base to the panel.

The dome light assembly weighs almost nothing and creating more work for myself in order to secure it in place was optional. I chose the easier alternative.



And this is the view from the inside. As you can see, there is at least a 1/4-inch of space between the top of the assembly and the cardboard, and this would provide enough clearance for the wiring.



Nevertheless, I applied two layers of duct tape to insulate the wiring and prevent a short circuit, as unlikely as that possibility might be.


I then installed and secured the dome light assembly to the T-bar trim panel and started reinstalling all the trim panels in reverse order. I also ran the second dome light wiring harness through the driver's side sail panel. Since there is enough space to fish the wire behind it, removal of the sail panel was (thankfully) not necessary.

I also used a couple of blade connectors to have the ability to remove the T-bar panel in the future without the need of cutting wires.


The photos above and below show the finished product. I bought a new replacement lens since the original one had yellowed due to age and the heat caused by the old incandescent bulb.


I temporarily connected the incandescent bulb to ensure everything was working properly. And you can see how dim it looks. It also gets so hot that it's impossible to handle, and it is surprising it does not cause additional damage. Personally, I consider it a fire hazard, so I ordered an LED bulb instead.


Old dome light incandescent bulb (top). If you're still using this type of bulb, get rid of it and replace them with an LED bulb (bottom).


The next three photos offer a graphic comparison between an interior without an overhead dome light, followed by the overhead dome light with a traditional incandescent bulb, and the third picture the dome light with the 6000k Bright White, 400 lumens, 1.5W LED bulb.




The photos don't do it justice, and also the fact that LED bulbs don't get piping hot is yet another reason to use one, not to mention their long-life compared to old incandescent bulbs.


One last comment about LED bulbs; they are polarity sensitive. In other words, if you install one of these bulbs and it fails to light up, remove it, turn it around 180° and it should work.

Installing an overhead dome light in your C3 Corvette (1968-1976) is a fairly simple yet involved enough process. If you decide to tackle it I suggest you get all the necessary components beforehand to make the project easier.

For those who want to keep the original storage compartment dome light, you can purchase a used or new fixture. Also, many GM vehicles used the same assembly so you don't necessarily need to purchase a "Corvette" dome light, so you may want to do a little bit of research on the subject. Needless to say, other similar dome lights may also work, so you don't have to limit yourself to a GM product.

If you buy the components separately, make sure that the base will include the bulb clips as they are specific to the base. You can always improvise a connection but in that case, all you're doing is creating unnecessary work for yourself. Get the right components and keep it simple.

One last thing. If you know what you're doing, this project can be done in three to four hours. Otherwise, allow yourself at least double the number of hours. And remember that you will also have to fabricate your own wiring harness to power up the light.


Adding an overhead dome light to your C3 Corvette is a great DIY project and one that you will enjoy for as long as you own your car.

Thank you for following my 76 Vette Blog!

1 comment:

  1. What a cool upgrade for the T-top C3's! Thanks for the detailed pics and instruction! A cool project I think most can do themselves if they're brave enough to start cutting into these 40+ year old machines! YIKES! I'll need to figure out some option for a vert with under the mirror lights or something!

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