Volvo Halogen to OEM Bi-Xenon Headlight Housing Swap for S40 and V50

This advanced tutorial describes how to re-wire the OEM Bi-Xenon headlight housings to work with Volvo P1 vehicles originally equipped with halogen headlights. The SKBOWE is tapped into the headlight harness outside of the headlight assembly and powers the OEM ballast, so no holes in the housing or cover are required.


Many years ago, I described how to re-wire the factory bi-xenon headlight assemblies as part of an project to facelift a ’05-06 S40 to the new style (’07+) front bumper and headlights with LED city lights. These assemblies are hard to find and very expensive, but offer a unique look (compared with pre-facelift and halogen-facelift) and are technically “DOT Approved” to pass inspection (as they are stamped D2S on the lens).

Note that this mod does NOT give you ABL (active bending lights) or auto-leveling functionality – the motors inside of the OEM bi-xenon housings remain disconnected and unpowered. THERE IS NO PRACTICAL WAY TO GET THIS ENABLED ON A HALOGEN CAR – you would need to change the headlight type in the CEM, add the leveling sensors (which is a lot of re-wiring) and pins in the CEM harness, plus the GDL modules. Sorry, short of creating your own system from scratch, it’s just not practical.

Unfortunately, the original project pre-dated the SKBOWE and the importance of the additional ground was not understood at the time, so eventually (within 3 years) the under-sized capacitor filters I provided failed and took out the WMM. However, with some tweaks to that procedure (described here) to allow using a SKBOWE, the process is just as safe as using an aftermarket ballast.

Install Process

There are two important mods to OEM equipment to make this mod work:

  1. The headlight harness (From the car, with the connector that plugs into the back of the headlight) must be modified to allow inserting the SKBOWE inline on the low beam wire; and
  2. Inside of the OEM bi-xenon housings, connect the pins that are missing in the halogen harness so that the OEM ballast can power up.

Step 1 – Tap Halogen Harness for SKBOWE

To avoid having to drill a hole in the headlight housing and having extra connectors (power in and power out) the cleanest way to get the SKBOWE inline with the low-beam supply is by tapping the OEM harness.

While it is possible to cut the connectors off the SKBOWE and crimp it directly inline, it’s better to just add a pair of 9005 connectors so that you can remove the SKBOWE in the future and go back to stock (just disconnect the SKBOWE and connect the male+female together).

Tapping pin 4 ground and pin 9 low beam with 9005 connectors to allow SKBOWE install outside of headlight housing
Modifications to the headlight harness to connect an SKBOWE without drilling holes in the headlight housing.

You’ll need to find two wires within the split-loom that goes to the headlight connector. you can do the tap anywhere along the split loom, in the image above it’s shown right at the connector for clarity. The pins are:

  • Pin 9 (+) – the low-beam power supply, green/white on my 05 (check your VWD to confirm)
  • Pin 4 (-) – the ground for the headlight housing

The female 9005 (“supply”) goes on the car side, the male 9005 (“output”) goes on the connector side. You can get the connectors for cheap by cutting up a 9005 extension. I like to use heat-shrink butt-connectors for this type of splicing, to keep everything firm and waterproof.

Step 2 – Prepare the OEM Bi-Xenon Headlight Housing

As shown in the wiring diagram below, the HID ballast in the OEM housing is grounded through pin 10 on the headlight connector, which is not populated in the halogen car-side harness. So inside of the housing, you need to connect pin 4 (the halogen and high-beam ground) to the wire that runs to pin 10 (the HID specific ground).

wiring diagram for 2007+ bi-xenon headlight housing s40 v50
Wiring diagram for the facelift S40/V50 bi-xenon headlight housing, 12V section (ABL/AL not shown)

The cleanest/easiest way to do this is by cutting the brown wire going to the four-pin HID connector as close as possible to the main headlight connector’s pin 10 (leaving as much length as possible) and then crimping it into the the the high-beam connector ground, which is visible if you remove the round cover on the top of the headlight.

Alternately, you could use another butt connector, cut the high-beam ground, and crimp everything back together.

Step 3 – Install the SKBOWE

The final step is to install the SKBOWE normally, per the installation guide, including the ground prep and mounting (zip ties or inside of wheel liner on bracket) – but instead of connecting it to an HID ballast, connect it to the 9005 connectors you added in step 1.


One Year Anniversary

That’s right, we are coming up on the one-year anniversary of the SKBOWE pre-order with 70 units sold and a total of 15,535 car-days (estimated) installed! To celebrate, the remainder of Batch 3 has been discounted to the pre-order price ($99)! Batch 4 later this year will be the last production run, so get yours while you still can.

AC vs DC HID Ballasts

A customer recently asked if SKBOWE was comparable with AC and DC HID ballasts, a confusing question because every HID ballast I’ve ever seen has been marked for 12V DC in, 85V AC out (bulb side). Turns out there actually are “DC” output HID ballasts, and they should be avoided as D2S bulbs are specified for AC drive only.

AC vs DC

As discussed on the issues page, HID bulbs are arc lamps that run a fixed current through two electrodes in a sealed quartz capsule. The voltage drop is about ~85V after ignition (20kV) and warmup. Like any arc lamp, electrons jump off the negative (-) electrode, and impact the positive (+) electrode, causing the (+) side to run hotter and wear out faster. To counter this effect, all OEM ballasts and most aftermarket designs send AC current to the electrodes, alternating each electrode between (+) and (-), so that both electrodes wear evenly.

Because the input power from the car electrical system is nominally 12V DC, there are two stages required to output the necessary power to an HID bulb:

  1. Step up 12V DC -> ~120V DC, using a boost converter with a flyback transformer, rectifier diode, and filter capacitor,
  2. Chop the 120V DC into 85V AC (RMS) using a set of push-pull MOSFETs (H-Bridge)

However, Chinese cost-cutters, in an effort to produce increasingly cheaper ballasts, figured they could get rid of the second step and feed DC directly to the bulb. The result is lower component count, but a bulb that will burn out very quickly due to rapid erosion of the positive electrode. It will also result in a lopsided, unstable arc that will “dance” and not locate at the center of the reflector foci.

Some Ebay Sellers are starting to market the difference, but price is almost always the most reliable indicator.

Some eBay sellers are starting to market the difference between AC and DC.

How to avoid DC ballasts

Price is usually a giveaway, though some manufactures have figured this out and are now up-pricing DC ballasts to make huge profits. Because DC ballasts are cheaper manufacture without the DC to AC stage they sell for very low prices, say, below $35 for a kit. AC ballasts require a large inductor and HV regulator for DC to AC conversion and are more expensive to manufacture. High-end Digital 35W AC Ballasts can’t be produced at that price, let alone sold for anything close. Without special equipment it’s hard to test at home, so make sure to order from a reputable company that specifies an AC output.

Also it doesn’t help for online shopping, but AC ballasts are significantly heavier than DC ones:

Weight of AC vs DC ballast


The what NOT TO BUY post has an example of a DC ballast. The Morimoto XB is an example of a good AC ballast. When I get some free time, I will update the ballast selection page with measurements from the ballast collection.

SKBOWE Batch 3 Ready to Ship

Of 25 units potted so far in Batch3, 12 have sold, and 13 are ready to ship! There are still two AL Gen2 bi-xenon pigtails available as well.

There are another 17 units of PCB assemblies ready for potting, but without an ETA on when they will be finished, they are being pushed to Batch4.

SKBOWE Batch 4 is ready to pot

When these are complete, I am waiting on 8 units worth of capacitors which are backorder until Mid-April, to round out all 100 SKBOWEs.  Based on average monthly sales, total remaining inventory should cover until October or November. After that, the future of the SKBOWE project is uncertain…

Batch 3 In Production

Batch 3 is on schedule for Feb 15 ship date! Building 40 sets this time, which leaves 10 sets worth of parts left in Batch 4 to experiment with different designs or for custom orders (harnesses, DRLs, etc).

Batch 3 – 80x PCBs fully assembled

Some fun stats about 40 sets of SKBOWE (80 units):

  • 320 wires cut, 640 stripped, 400 soldered
  • 400 capacitors + 240 diodes + 80 resistors = 1440 leads soldered
  • 80 heatsinks cut and bent, 80 enclosures notched, 80 covers taped
Bending the heatsinks for batch 3

After stuffing the enclosures (heat wire, form wires, tape wires, then test-fit heatsink and insulator), it’s time to mix up some potting compound.

Stuffing enclosures, prepping covers

Then each one gets a thin layer of compound, board goes back in, another layer of compound, cover gets glued and goes on, then the whole thing gets wrapped with electrical tape to compress it. Once all of them are done, into the oven for 2 hours at 165F.

Baking the first potting pour of Batch 3

I ran out of ABS cement (more on order) so for now there are 11 (so the 9 pre-orders will go out on time).

Stay tuned for more updates!

SKBOWE Batch 2 Sold Out, Batch3 open for Pre Order

Batch 2 Sold Out!

Wow! Hard to believe but all 50 of the original Batch 1 / Batch 2 SKBOWEs have sold in just 6 months. They have shipped all over the US, as well as Canada, the UK, Ireland, Germany, and Netherlands. While there were 16 units in the initial pre-order, sales have been stronger than I expected, averaging 6 units/month from August onwards.

Batch 3 / 4 open for Pre Order

It’s sad to see the bin empty, and thinking of the stories that I have heard I can’t let it stay that way – so I have decided to go ahead and order parts for another 50 SKBOWEv2. Again, some the capacitors are backordered so there will be a Batch 3 shipping in February and Batch 4 shipping some time after that. The pre-order is open now if you want to guarantee yourself a set.

Looking Forward

The original SKBOWE business plan called for 100 units total, and at this time it looks like Batch 4 will be the last of SKBOWE v2. There are several ideas for features to SKBOWEv3, such as a removable harness and a DRL detector, but the design is still tentative. I guess for now, you’ll just have to wait and see!

AL Gen2 Projector Pigtails in Volvo OEM Colors

I found the connectors that AL use on their bi-xenon projector solenoid control boards (Mouser #571-2-1718346-1 and #571-965906-1-CT) and ordered a few to make pigtails that connect the high beam solenoid into the factory wiring. The OEM connector locks securely into place, and the 12″ (30cm) automotive GXL wire is designed to hold up inside of the headlight housing. Wire is color-coded to match factory wires (yellow = +12, brown = ground) to ensure correct polarity and not look out of place inside of the housing.

AL (OEM) Salvaged Projectors

Image of projector pigtails in brown and yellow wiring
Custom made Volvo OEM color AL projector bi-xenon solenoid controller PCB pigtails.

Most used (salvaged) projectors come with short (cut pigtails) of various colors or no harness at all. I have never seen a set in yellow and brown, the wire colors used in the Volvo headlight housing for the 9005 high-beam connector.

If you want to wire up a projector retrofit without using messy splitters, I am selling these for $20 shipped (Priority Mail) to the US, or $12 with your SKBOWE order (just contact me first!) anywhere. Each order comes with a pair (2x) of 12″ GXL pigtails and four (4x) 4″ black zip-ties to match the OEM internals. You will need to provide insulated butt-style (if you cut-and-splice) or 9005 female (join inside of the high-beam connector) crimps – see this post for details.

Replica Projector Pigtails

Replicas use the same connector but a different pinout: the yellow wire is on the center (pin 2) rather than on the end (pin 1). All new replica projectors come with pigtails, usually white (+12) and black (ground). These will work fine, but if you want to go for a 100% OEM look, you can order a set of these color matched pigtails and swap the pin across. It is pretty easy to swap the pin over using a jewelers screwdriver. Or let me know first and I’d be glad to do it for you.

Ballast Testing: What NOT to buy – $20 eBay Kit

This is a post about things you should NOT buy. Please DO NOT BUY things on this page.

I’ve noted that the SKBOWE will work with just about any HID kit, but when it comes to choosing a kit, there is a difference between “can” and “should”. The old adage “you get what you pay for” is very relevant, so avoid listings like this one:

eBay auction listing of what to avoid
An example of what *not* to buy for your Volvo

Of course, I couldn’t help myself in seeing how they could possibly sell an HID kit for less than a single D2S bulb, so I put in an order and the kit arrived 7 days later:

Warning Signs to look for before installing HIDs

If you observe any of these warning signs, you should not install the kit. They are easy-to-recognize:

Warning sign #1 – It was cheap. Obviously, at under $20 for 2 ballasts and 2 bulbs, this was not going to be top quality. The Kensun (Amazon) brand kits are $60, and are significantly better than this.

Warning sign #2 – It feels cheap. The first thing I noticed was the weight of the ballast – it feels like an empty case.  My postal scale says 3 Oz (85g), including the internal ignitor! Compare to the Morimoto XB35 at 10 Oz (295g). This is a DC ballast design, so even if it did work the bulbs would wear out very quickly.

Warning sign #3 – It looks cheap. Crummy sticker placed off center with no brand name, “input corrent [sic] : 10A” (this would be 135W, BTW). Back side has wood screws holding an aluminum plate onto the plastic case, didn’t bother to countersink so the heads are proud of the surface. No weather sealing whatsoever. No strain relief on the output cord (it looks like there is a nut, but it is cast and part of the case, the wire easily slides in and out).

Warning sign #4 – It’s built cheap. The internal construction of this ballast is actually scary, reminds me of the counterfeit usb chargers that routinely cause fires – but this is running at 5000 times more volts! No potting or through holes, which will shred this in an automotive environment. Integrated ignitor with no insulation. Random transformer rather than an actual boost converter. This is a disaster waiting to happen.

Guts of a super cheap HID kit.

Please do NOT use this type of kit in your Volvo (even with the SKBOWE)! When there is talk about “EMI” issues, it is these sorts of ballasts that are to blame. Any decent company producing a reputable ballast will be 100x better than this garbage.

Honestly, I am not even sure I want to hook it up to the testbench. But if the SKBOWE can run this, it really can run anything! Stay posted for an update with electrical performance.