Posted on

Seal Headlights Like a Pro

Seal Headlights Like a Pro

Get a good quality Butyl sealant such as OCI, or even better Morimoto RetroRubber. I was using OCI until the RetroRubber came out, and it’s a much better product for sealing headlights. OCI works alright, but is made for windshields and doesn’t dry the way RetroRubber does. It stays kind of gummy. When RetroRubber dries, it’s more rubbery and was designed specifically with headlights in mind.

Re-sealing is much easier than removing. You need an oven, heat gun, flat head screwdriver, heat-proof gloves, and lots of clamps.

Some information about condensation. Condensation isn’t necessarily caused by a bad seal. It happens because there is warmer air on the inside of the light than on the outside of the light. If the headlight is just getting a little moisture on the lens you can add vents and cover with 3M Goretex patches.

If you actually see water pooling or large droplets, you might have a leak and need to try again.

Step 1:

Set oven to 240F.

Step 2:

Smooth out the old butyl glue.

Smooth out the old butyl glue if not removing it. I use a heat gun to warm it a little and a flat-head screwdriver to smooth it in the channel.

Step 3:

Stretch it out so you don't overfill the channel

Add a string of new butyl or retrorubber to the channel. Stretch it out so that it’s thin, because too much butyl will prevent the lens from seating deep enough into the channel.

Push the lens in place until it sticks on its own.

Step 3:

Protects the plastic from the metal oven rack

When the oven is heated, put the lights on a baking sheet, grill protector sheet (I use Yoshi’s from Bed, Bath, and Beyond), or damp towel so that no metal in the oven is touching any plastic on the housing. Set a timer (I always set 2) for 10-15 minutes.

Step 4:

Use some thick gloves to get the light out of the oven and push the lens in as far as possible.

Step 5:

Clamp the lens into place.

Start clamping the edges. Add clamps wherever you possibly can. The more the better. Good time to reinstall any screws or clips that help keep the headlight lens in place as well. Wait for it to cool down, and it’s good to go.

Posted on

DIY 12V Power Supply for Testing Headlight Components

If you are going to be testing car electronics and don’t want to have to install them on the car every time you need to test something you are going to need a 12V power source.

A cheap, easy, and flexible way is to use an old ATX desktop power supply. These have multiple +12V outputs that work great for testing headlight components. I can light up highs, lows, and other accessory lighting in a headlight simultaneously.


  • An ATX power supply for a desktop computer
  • A toggle switch
  • Quick connectors, solder and soldering iron, or Suitcase taps
  • Heat shrink or electrical tape
  • Step 1:

    Find a power supply. Being a Computer Engineer, I always have spare computer parts laying around because you never know when you are going to need them, right? So I was able to just pull one from an old tower I had laying around. It’s nothing special, just a 250W ATX power supply.

    Step 2:

    Find out the +12V wires. Should be all the yellows, there should be a label someplace on the casing that says the output values of the different colored wires.

    Step 3:


    Find the wires that run to pin 3 and 4 of the ATX connector. This is the power wire that the power switch for the motherboard uses to turn on the power supply. In the above picture, it’s the green and black wires you see clipped and spliced. We need to attach a toggle switch between these two wires to make it easy to turn on the power supply. You can just splice them together, but then you have to plug in and unplug every time you want to turn on or off.

    Step 4:

    This step is technically optional. I actually didn’t do it until I decided to write this up. Now that I have this convenience, I don’t know why I put it off so long. Adding a toggle switch or button to control the power. You just need a switch or button that stays on or stays off for this. I used an aftermarket fog light relay button. They will have 3 terminals. You will need to ground 2 of them and run the power wire to the wire that was on pin 4 of the ATX connector.

    Step 5:

    Plan your connections and solder/splice them in place. There are adapters for 9006 to just about everything else and since I’m a dealer, I have all those adapters so I soldered up two of my +12V outputs to 9006 pigtails. This won’t work for everything though, sometimes you need more flexibility so I recommend keeping a couple for using with alligator clips. This way you can just clamp on to unusual connectors, swap the power from low to high on a dual filament bulb, or send power to individual headlight housing pins.

    Step 6:

    Clean up. It’s a real pain to move a power supply around with all those wires hanging off it. Chop off all the wires you don’t need. Tape or shrink wrap all your solder joints and exposed wires.

    Posted on

    How to Open Butyl Sealed Headlights

    How to Open Butyl Sealed Headlights

    Tools Required

    1. Oven
    2. Heat gun
    3. Wide blade scraper
    4. Thick gloves
    5. Damp towel or grill protector sheet

    This procedure works on butyl sealed housings. Permaseal is not covered here.

    Opening headlights isn’t an exact science and you can ask the internet, “How long, and what temperature should I bake them at to open them up?” and you will get 10,000 different answers. There is a pretty common range given though which seems to be between 220 for 10-20 minutes up to 270 for 8 minutes.

    General Procedure

    1. Set oven to 240F.
    2. Remove bulbs and metal parts from housings
    3. When the oven is ready, lay the towel or sheet on the rack and put the housing on top. Be careful nothing is toughing any of the metal in the oven.
    4. Set 2 timers (I always set a backup) for 10 – 20 minutes.
    5. Get the housings out when done, and push the wide blade scraper into the groove between the lens and housing.
    6. Start prying the lens away from the housing. Work your way around. Don’t try to go too fast. Get it separated a bit, then move a few cm’s away and start prying again. Some people use a screwdriver for this part, but when you mix a narrow, sharp blade with heated, soft plastic, the plastic is going to get damaged.
    7. As you get one end pried away, you’ll notice the butyl strings off like cheese on a pizza slice. Once it starts to cool, it will start to harden again, and really holds on. If that happens, I use a heat gun on the lowest setting to melt it. You could also use a razor blade; I have done both, but I prefer the heat gun because the glue just shrinks back to the channel or lens instead of falling in and possibly sticking to the chrome.
    8. Eventually, you will be able to just pull it apart with your hands.


    • If you get the glue on your lens and it’s plastic, use “Goo Gone” not “Goof-Off” to remove it. The UV coating will come right off with Goof-Off if you press too hard. First try to just heat the lens again and rub it off with a finger or thumb. If that doesn’t work, use only a very light brushing of Goo Gone, there is no need to push down at all, the solvent will do all the work for you.
    • Using a screwdriver can break or deform the channel that the lens fits in; I use a wide-blade paint scraper for all my prying, and .
    Posted on

    Disabling DRL at Switch on 99-05 VW Jetta

    Disabling DRL at Switch on 99-05 VW Jetta

    MK4 Jettas leave the factory with a bi-halogen (dual-filament) headlight bulb. Since the car has only one main beam, and the the daytime running lights run off those same bulbs, you need to disable the DRLs to install HIDs. The reason being, that the DRL runs the light at 80% power and that will destroy HID ballasts rather quickly.

    There is an easy way to do this that simply involves bending a pin down in the connector of the headlight switch. The pin will be labeled TFL and will be in different locations depending on whether you have a US-spec or European-spec headlight switch.

    The US-spec switch looks like this:

    The European-spec switch looks like this:

    Step 1: Remove the Headlight Switch

    To remove the headlight switch you push the dial in, and turn it clockwise like you are turning on the lights. Once you can’t push it any further, you pull it out towards you.

    Step 2: Unplug the Headlight Switch

    Put your fingers at opposite sides and wiggle the plug side-to-side until it comes out. There is no trick here, it just comes out by wiggling it free.

    Step 3: Locate the TFL Pin

    On either switch the TFL pin is the 3rd one from the edge; depending on how you flipped it, this can vary. The thing to note, is that the pin is labeled “TFL” no matter which switch you have.


    Step 4: Bend TFL Pin Flat

    Now use a flat screwdriver to just flatten the pin so it looks like the picture in step 3.

    Step 5: Plug it Back In

    Plug the switch back in and verify that it works. If your dash lights didn’t come back on when you plugged it back in, it’s either not plugged back in all the way, or it’s upside-down.

    If your dash lights came back on and all the turn signals and everything appear to work, then with the headlight switch in the off position; lower the parking brake if it’s engaged, and if the headlights don’t come on, you are golden. Now you may go ahead and hook up your HID relay without damaging your ballasts or bulbs.