Tuesday, April 2, 2013

DIY: Tail Light Modifying

Today we're going to completely take apart a Hella/ In Pro "all clear" tail light, which is intended for a MK4 Golf/ GTI.

Along the way, I'll show you how to do the following:

-Prep the tail light for paint
-Separate the lens from the tail light housing
-Repair the lens and housing
-Modify the housing for different effects

I'll be using my set of Hella's, which I've already taken apart and modified once over. These typically sell anywhere between $100-$200 (used), $250-$300 (new), and are a great template for color applications.

Photos courtesy of DaveLinger

Let's begin by taking a look at my set:

The first go-around, I decided to make an "all amber" tail light, or what translates into: Left: A/A/A/C -- (amber, amber, amber, clear), Right: A/A/A/A -- (Amber, '' , '', '' with the reverse light clear). Originally, the plan was to offer a truly all-amber tail light, but early on I noticed the definition of the dividing lines, and thought a clear bar was too good to pass up. The result was a wacky concoction, featuring a space for a reverse fog light on the left side.

I'll admit, at first I had no intention of taking them completely apart. But after I started sanding, I noticed they were covered inside and out with exhaust debris. This meant finding a way to break the tail lights down completely - a process I'll explain later.

Let's Begin the Tutorial!


You want to start by wet sanding the lenses of the tail lights. NOT dry sanding, mind you.

Here's the route I took, where by wet sanding in grit stages:

-2,000 (after paint and clear)

It's important to know that while the tail lights are structurally sound, they can still encounter problems based on their overall shape and design. I've outlined the areas that are most problematic here:

Consider that the biggest issue with these tail lights is that they tend to break at their corner. The edge is so sharp that if dropped, both the housing and the lens can fracture. It's therefore a good idea to lay a towel out at your feet, so as to not potentially waste hours of work.

Positioning your hand at the base of corner helps reinforce its brittle edge while sanding. Also make sure to apply as little pressure as possible in this area.

The second problem areas are the "dividing lines" -- the thin lines outlining the bars. You have to imagine the tail light lens as a stamped set of layers, with the line running all around the inside as the thinnest point between each layer. Some of them are reinforced however, and you can apply a little bit of pressure.

If you apply too much pressure however, the bars themselves can separate. The result is a hairline fracture that allows moisture to become trapped behind the surface of the lens.

The most appropriate way to start is by tackling the edge at the top of the lens -- this is the area which is most reinforced. From there, you can move on to the face of the lens:

Sand each bar a section at a time and remember to avoid crossing the dividing lines.

There will come a point when you'll have to go over each dividing line, and the position of your fingers will help you through this process:

Keep your finger tips on either side of the line, and allow the sandpaper to lightly touch the surface.

One thing you'll notice about most tail lights (especially the aftermarket variety) is they're littered with manufacturer stamps. This is extremely helpful if you're looking to invest a lot of time to sand it proper.

-Tip: Use the manufacturer stamps/ dots as a guide for wet sanding.

Believe it or not, you can sand them out completely. But it takes a LOT of work. The HELLA logo is suprising easy, but along the surface of the tail light you'll notice three recessed dots. The first is mid center on bar 1, the next two are on bar 4 -- one in the center of the reverse light, the other on the opposite side. To ensure the surface is completely smooth and flush, you need to sand them completely out. If you sand them the correct way, you'll have done your job in the very first stage of prepping.

Lastly, it's probably a good idea to hit the underside of the lens, shown here:

It doesn't need to be perfect, but use your best judgement and sand accordingly. It should be scuffed up enough with 250 and 400 for paint.

*However, make sure to avoid sanding the area where the lens and housing are married together as it has the potential to separate. If it does, don't worry. I'll explain more in the next section.

Assuming you've sanded each section appropriately, it would then be time to paint. But you have an option -- you can remove the lens from the housing and paint the lens itself, or tape off the housing and spray the lens in one piece. If you go the first route, here's what you'll need to do:

Separating the Lens From the Housing

Let's look at the photo above one more time:


If we take a close enough look, we can see where the lens separates from the housing. If you sand down this section enough, the lens will naturally pull apart from the housing. (See on the far right side?) This is the best place to make your first incision.

Here's another example of where the two separate:

Now, with removing lenses from housings, there are two approaches you can take for overall separation:

-Heat the manufacturer sealer/ silicone with a heat gun.
-Place the entire tail light unit in a household oven.
-Separate at room temp.

What ever method you choose, know that the manufacturer's sealer isn't very strong and can pull apart fairly easy. Silicone that has been applied to the lens -on the other hand- cannot -- it needs to be heated for removal.

After you heat the area, use a utility knife and penetrate the gap between the two. Don't be affraid to apply a little force at the base of the housing. Keep in mind, it's really hard to break the lens with the utility knife - even if the end of the blade is pressed up against the inner wall of the lens. Be more concerned with dropping the whole tail light or inflicting damage on yourself.

*Can you tell what's wrong here? Always make sure one hand is reinforcing that sharp corner, and be extremely careful.

Follow the curvature of the lens until you've made an incision completely around. Then, prepare to pull it apart.

The key to separating the lens from the housing is to pull outwards; i.e. bottom out towards you/ top out towards you. NEVER from the left or right sides.

*Pulling from either side puts pressure where the tail light bends most, causing it to crack. If it cracks, don't worry - we'll talk about that next.

This is the tail light with the lens removed. It's interior has been slightly modified from the first time I took them apart.

Repairing the Lens and Housing

Lets say hypothetically (or in my case, realistically) you've cracked the lens. The good news is, the lens can be resealed, but only up to a certain point.

All you really need is a plastic-friendly resin. In other words, something capable of seaping into the crack, strong enough to bond and transparent enough to cover up the excess damage.

If the housing happens to break, you're going to need a stronger type of resin/ bonding agent. Believe it or not, if the lens is in good shape, most people will throw out the fractured part of the housing and put them on their cars, damaged. Technically, the lens is nearly pressed against the body and bumper of the car, so it's not likely something will get inside the tail light, but I still think it's lazy. Grab an epoxy and mold the housing back together.

Modifying the Interior of the Tail Light

So the hard part is over. Now -if you choose to do so- you can customize the inside of the tail light housing.

The logic here is that whatever color you apply to the interior will affect the exterior color of the lens. A good example is the most modern tail light/ head light design.

I started to notice that they weren't simply filled with red plastics and reflectors, they contained silvers, greys and black colors as well. The result is an amplification of the exterior color. We'll use mine as an example.

Notice closely that the middle of bar four originally had red plastic reflectors. Depending on your state/ country's tail light qualifications, most require a red reflection up to a certain distance. In Arizona, it's expected that an officer see the red in my tail lights from 50 feet.

Bare in mind, however, that the bulb itself is red, the sleeve the bulb fits into is red. This means you can minimalize the color combinations and you won't be breaking any laws either. Hard to believe, but the amber tail lights were actually legal in my state. Although bright orange in color, they didn't take away from the red at its base, which was visible up to the legal distance.

The plastic reflectors are tacked into place on the top and bottom of the interior, making them incredibly frail. A tiny screw driver applied right at the tack molding will dislodge the reflector completely.

The interior housing doesn't require much sanding or professional grade work. Simply use alcohol and tissue paper and wipe the area you decide to paint. I've chosen a metalic silver, because I'll be painting the lenses "all-red".

The pictures above are from the first go-around. You can see the effect a mild silver leaves on a clear surface. This time, I'm going to try using a more metallic silver for added effect. Here you can see the early results:

I'll be using House of Kolor's "Kandy Apple Red" on the lenses. In this instance, I think it best to work with contrast. Consider that the result will be a uniform layer of paint on the surface; i.e. no textured look of the dividing lines. I intend on using an entire spray can of HOK with the idea to "hide" all that silver, in mind. The logic here being that the silver is so bright, that I need to enrich the surface with so much paint to compensate. Make sense?

Keep in mind, people "paint dip" lenses -- they completely submerge the lens into a vat of water and paint and they turn out transparent and perfect. You can virtually use an INSANE amount of paint before it loses its transparency, so don't be affraid to bury it!

-It's basically the same technique. In fact, at Wustefest 2010 I ran into someone with the same set of Hella's -- except they were remarkably red. He explained how he used this dipping concept to acquire the full effect.

So here's the end result. I admit I jumped a few steps ahead, but I'll be sure to explain all the details. After buying the paint and clear coat, I had a friend professionally shoot them.

Obviously, if you've completed the last step (separating the lenses from the housing/ prepping the lenses for paint), you'll want to tape off the exposed area of housing, shown in black:

I recommend using SEM's exterior Trim Black. You can apply as many coats as you like and it's virtually problem-free.

Simply mask off the surrounding areas -the lens and the back of the tail light- prep with alcohol or metal pad, and paint.

Finally, use a clear silicone adhesive to bond the lens to the housing. I recommend the one featured here:

Make sure to apply it to the sections you cut into to remove the lens:

-The bottom of the housing doesn't matter so much as the top and edges. Trust me, you might think you have enough, but as soon as it rains you'll be seeing spots inside the housing.

-Make sure to be thorough, but don't over do it.

Use a finger nail to clear out the excess silicone, clamp the lens and housing and let it sit overnight.

That's it!


  1. We are dealing with New Japanese Truck Spare Parts for taillights, Mitsubishi Trucks, Toyota Dyna, Hino Trucks and Nissan UD Trucks in Australia.

  2. hi Shane, good job on the lights. They looked sick! any chance you could make some more? I am in the UK. I can make a payment through paypal etc. let me know by responding to this comment and I'll be sure to check back.