Appendix “I”: Upgrade, Installing Xenon High Intensity Discharge (HID) low-beam headlight bulbs

Disclaimer: The content of this document relates to the Porsche 993 (911 1995 to1998) I am not a professional automotive technician and some of the opinions expressed in this document are just that, opinions, therefore, please feel free to use this document at your own risk. Many times a lot can be learned by simply watching qualified professionals work on your 993

Appendix “I”:

Several years ago I updated my existing low beam bulbs with a 6000 degree Kelvin HID Xenon kit. It seems that most of the aftermarket kits are very similar. To do a minimally invasive job you will need a kit with the “slim” or smaller ballast that with a little DIY engineering can be mounted inside the headlight pod. The installation is relatively easy as all the components will fit in the lamp housing unit. 

The high voltage wires that come with the generic kits are designed for general installation and so are longer than needed and so must be bundled in the housing. Some recommend you do not try to shorten these wires as any voltage leakage caused by reinsulating them may cause the bulbs to not ignite. Others have shorted them with good success. An option is to use a kit specifically engineered for a clean install from bergvillfx.com.  In any event, do bench test any modifications to the wires by trial firing up the lamps with the alterations in place. With the long wires, the install does not look too neat inside the housing but it has been working reliably in my case just fine since 2008.

In the kit I used, the 12-volt electrical wire terminals leading to the original halogen bulb could be used to connect the HID system. No cutting or splicing.

Headlight Pod

Headlight Lens
In Frame

While the lamp pod is out one can consider cleaning the reflector and inside face glass. If the glass face has never been removed previously the clips surrounding it are factory melted and so fused to the pod body.

Headlight Pod
Clip Location

The fused section can be ground off with a moto-tool or cut loose with a utility knife. The clips can be brittle so one or more may crack when releasing them. This seems to not be a big issue as the glass facia seems to hold on well with a cracked clip or two. When reassembling there is no need to remelt the clips, they hold on just fine by spring action as is. 

If you decide to clean the mirrored reflector use a very soft and clean microfiber cloth such as used to clean eyeglasses as it is easily scratched. I also recently came across a chrome paint maker that may be useful in touching up the mirror-like reflective coating inside the headlight pod. I have not tried this product but it seems promising for repairing mirror reflective coatings on glass or plastic. I would test it first and evaluate the results before trying it on a lens pod reflector.

https://www.arromark.com/manufactured-product-lines/flomaster-mirror-finish

Also, there are services that rechrome plastic parts that can produce a mirror-like OE finish.

I hear all sorts of discussions about needing a larger fuse for the 35W HID bulbs because the system is supposedly hard on the existing power switches during initial loading to ignite the bulbs. I did not choose to address this issue in my installation because in my understanding switch wear comes from the spark as the result of the transition to open (off) not transition to close (on). In other words, a switch can withstand a lot more load on close than open. When the plasma-based lights are turned from on to off they are lit and warm so the load and therefore the stress on the switch is lower than with the original 55 Watt H1 halogen incandescent lamps. It seems to me that this lower demand should render the need for a more robust powering circuit moot. (7/10/2021) -- Now that the aftermarket xenon bulbs have been in my daily driver for 13 years, I have not experienced any reliability problems with the headlights.

Special care should be used when aiming the headlights after the installation. I used the USA DOT aiming procedure that can be found on several websites. When I did this I found that oncoming cars would flash me thinking my headlights are on hi-beam. Blinding opposing traffic probably cancels out any safety advantage of having brighter daylight color bulbs. I lowered the aim of my headlights slightly below the DOT specification and other drivers stopped flashing me. Here is a page that discusses aiming headlights once an HID kit has been installed.

Here are the gotchas on this job.
1) Regardless of the brand many times HID bulbs/ballasts kits are Dead On Arrival (DOA) out of the box and so should be powered up and bench-tested and proven to function before you install the components in your car.

2) The way HID lamps work is a very short 18,000 to 35,000-Volt spike (trigger) is sent to the bulb that causes the gas in the bulb to form a plasma and ignite. Then the supplied voltage drops back down to 85 Volts or so that sustaining the plasma state. For this reason, bulbs may not ignite reliably if there are any electrical grounding leak issues on the bulb or its feed wires that diminish the initial pulse. This means any dust, dirt, or moisture that may be inside the headlight pod should be cleaned out before installing the bulbs. Also, brand new bulbs will sometimes not light off on powering up every time so cycle the headlight switch again to light them off and run your headlights for a short burn-in period to season them before concluding something is wrong with your set-up.

3) The xenon bulbs that come with the HID kits sometimes have a slightly oversized glass envelop diameter making it difficult to slide easily into the bulb socket. I had this issue and just reamed out the socket diameter very slightly with a mini-grinder to allow the bulb to fit.

Dremel Mini-Grinder

This doesn't damage the socket or cause it to become incompatible with an original H-1 Halogen bulb or its HID replacement. Some have suggested that this issue may only appear with earlier production cars. If you do end up reaming out the socket some suggest holding the lamp pod with the pod housing back facing down so any debris created from reaming falls out of the fixture rather than into it. In any event, be sure to vacuum up the dust & debris it creates to avoid it from interfering with the bulb's ignition.

4) Getting the headlight pod back in and the electrical plug lined up can be a bit of a trick.  By spraying some Teflon or Silicone lube on the headlight pod's mounting tracks the pods should slide right in. Also, rub some of the lube with your fingertip around the edges of the electrical socket to help it in fully seating as well.

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