By on March 21, 2012


Confused in South Bend writes:

Hi, Sajeev….

I am the owner of 2003 M-B C240 base, with the Bi-Xenon headlights. Recently, one of the headlights has developed an issue….in cold weather, it does not work.

Went to my German car specialist, who wasn’t so special on this issue.  No problem, he said, replace the bulb.  $160 later, still had the problem.  OK, negotiated for him to give me a credit on the next fix.

Researched on the web, purchased a used Ballast.  Mr. German car specialist looked at the part, scratched his head and said, “I don’t know what this part is.” Mercedes dealer says, spend about $900 for an entirely new headlight assembly.

I know that Mercedes engineers think money grows on trees….but $900 to fix a balky headlight?  Come on…

I want to get this fixed….my question, is replacing the ballast the way to go?  Or must I render to Stuttgart…..?

Sajeev answers:

When one HID headlight goes out, the ballast and/or the bulb is usually the problem.  And I would never just buy a new HID bulb just to take a stab at the problem, especially when we know the quality of electronic components in German vehicles of this vintage. Who knows, maybe there’s a lighting control module mounted elsewhere that we non-German-techie people don’t know about!  This is what specialty shops are supposed to do for us!

But, unfortunate diagnosis aside, I still think the smart money is on a bad ballast.

A visual inspection of the bulb is necessary, and the ballast is first tested by checking for power to the ballast itself.  If you got nothing there, bigger problems away from the headlight assembly are in your future. If not, get the ballast tested and repaired/replaced. I am by no means a lighting guru, but from what I see via Googling, you can’t test a ballast with your garden variety multimeter. A specific tool is needed.

You made the classic mistake: buying a part and hoping for the best.  Find someone who knows what they are doing to test and verify the actual problem. From the sound of it, you need a new German Specialist.

Send your queries to [email protected] . Spare no details and ask for a speedy resolution if you’re in a hurry.



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32 Comments on “Piston Slap: Going Ballast-ic on Bi-Xenons?...”

  • avatar

    Uhm, wouldn’t the cheapest thing to do is test out the stuff that’s already there? Move the “bad” bulb to the good side. Does the cold running problem move with the bulb? Then it’s the bulb. If not, try moving the ballast to the other side. Does the problem move with the ballast? If yes, replace the ballast, if no, it’s not the ballast and as Sajeev notes it’s another lighting module buried deep in the car. At that point do some more internet research cause your mechanic is worthless.

    • 0 avatar

      +1 Thats what ya try first. As these cars with Bi-Xs age, there will come a time when fixing/replacing may/will be more than the cars worth. There may be a market for retroing H7s into these things…a bulb and 12V.

      • 0 avatar

        You would need a whole new lens assembly in most cases, too wouldn’t you? Still would probably be cheaper than the HID parts, though!

      • 0 avatar

        You indeed will need a whole new lens/reflector assembly as the optic pattern of the lens or reflector will be significantly different for arc discharge type lamps than for halogens.

        The same is true for transverse halogens and parallel filament halogens, so it pays to know what your car comes with and get the same or similar type bulbs for it to keep the proper beam pattern and reduce glare.

    • 0 avatar

      As a Benz tech thats EXACTLY what I would do to diag it at the dealership. Try the new ballast (iirc the bulb is actually plugged into it), if its not that you’ll probably need the headlamp.

  • avatar

    Ballasts are affected by cold weather. The German non-specialist can’t be expected to know this from birth but he could have tested the output from the ballast when it was cold and made a determination it was not providing any voltage. Assuming he knows what voltage is and how to use a volt meter. Don’t assume he does.
    I see this a lot, troubleshooting with a credit card instead of the right tools.

  • avatar

    I would think you could at see if you can rebuild the ballast yourself. They do have kits out there. May apply, may not.

    • 0 avatar

      My Bi-Xenons have a mechanical feature that moves an obstruction out of the way of the low beam xenon to allow it to shoot more light upward to augment the high beam lights. Could this have failed? Additionally, mine self level and corner, which is also mechanical and nature.

      • 0 avatar

        Do you actually have a separate high beam as most bi- projector lamps will use a moveable shutter to create the high beam by blocking the lower portion of the bulb’s light as it’s a single filament, or arc in this case for Bi-Xenons.

        For separate high beams, the shutter is fixed and the bulb goes off for the high beam if I’m not mistaken in a quad headlamp setup.

  • avatar

    “I know that Mercedes engineers think money grows on trees….but $900 to fix a balky headlight? Come on…”

    “Confused in South Bend” was the shiznit, now people just laugh because they see a MB with a busted headlight owned by someone who can’t afford to fix it.

    Happy motoring.

  • avatar

    That’s pretty low for a Mercedes HID ballast actually. I’ve seen Nissan and Cadillac ballasts go for well north of a grand. Cheapie Chinese aftermarket knockoffs are about 1/4 of the cost and 1/4 of the quality.

    Be advised that this simply your fancy German car sending you a gentle warning that you’re about to start sending a Große amount of money on your expensive luxury automobile.

    • 0 avatar

      For close to a grand I hope you mean the whole headlight assembly. BMW lists their ballasts for $450 or less, and you can find OEM parts for under $300 online.

      I’m not saying that’s chump change to get a headlight working, but I really hope Mercedes, Cadillac, and Nissan don’t actually charge $1k for just a ballast.

  • avatar

    People buy used German cars for the prestige, then freak out over the repair bills…. Reminds me of my neighbor trying to work on his recently purchased 05’ish BMW 5 series with a autozone special 50-piece tool set. Last time I checked, it still doesn’t run “quite right”.

    First, as a technician myself, your mechanic sucks. Second, if spending $900 on a headlight is cramping your style, then go buy a Toyota.

  • avatar
    Educator(of teachers)Dan

    Reminds me of a certain member of the B&B who always says “Never buy a used luxury car…”

  • avatar

    $900 sounds about right for that vintage/marque. 1999 to 2003 Acura TLs and CLs (that over time WILL NEED HID ballasts and/or ignitors) run about $800 (before labor, without the bulb which is about $200) where I work. This is also why I will likely not own a car with HID headlights I cannot ‘down-convert’ to halogen.

    Bonus: A guy I work with ‘obtained’ an aftermarket HID kit from a Civic hybrid that was traded in; he then sold it to another coworker to put into his Trailblazer. The ballast malfunctioned and fried the leads going into the bulb. Needless to say, he didn’t end up buying them.

    • 0 avatar

      Don’t ever, ever, ever, ever, ever (seriously ever) mess with any kind of wiring on a Trailblazer or any other vehicles in the GMT 360 family. I cannot stress this enough.

      Even the stock wiring harness for stock halogen bulbs won’t lass more than a few years before frying out. Adding aftermarket “high wattage” bulbs or cheapo HID kits will leave a blackened pile of expensive meltyness under the hood.

  • avatar

    Do any new vehicles still use sealed-beam headlights? I know that the Ford E-series vans and work trucks did up until recently. You can buy a whole new headlight for $20 or less with those.

    • 0 avatar

      Add the Chevy Express van to that list as well.

      You can still get a fleet series Ford Work Truck model with sealed beam lights too.

    • 0 avatar


    • 0 avatar


      Maybe Colorado work trucks (previous Gen). Maybe Chev cargo vans, although I think Ford may have switched over after the last body ‘refresh’.

      Ranger comes to mind, but since they aren’t built anymore, Who TF knows…

      Maybe something built in China or India?…

  • avatar

    My recollection is that a lot of European car ballasts are essentially the same. Maybe that was a time in the past (I seem to recall that the ballasts in my Saab 9-5 were the same as those found in a bunch of BMWs and Cadillacs.)

    Having said that, I know BMW owners had a lot more ballast issues, because the BMW has an auto light system that turned the lights off and on all the time, which wore out the ballasts.

    Does anyone know of any ballast rebuilders? I see there are rebuild kits online, but I imagine some reputable company is rebuilding these for a lot cheaper than a new one.

  • avatar

    I had this same problem on my 2000 S500, which had otherwise been surprisingly free of problems.

    There are some things, such as HID headlights, that seem best left to dealers. We went to one of our area’s few Mercedes specialists, a hobbyist type who had about 50 “project” old cars in his lot. Bad mistake. We spent about $500 with him trying to solve the problem before it became clear he didn’t know what he was doing. The end solution was a $2,500 bill from the dealership for a complete replacement headlight assembly.

    One problem with these cars, which I think has not been covered here, is that expertise is easy to find in areas where the cars sell well (i.e. Los Angeles, Palm Beach, etc) as opposed to places where they sell poorly (i.e. Pittsburgh, Detroit, etc). If you find someone good in an area where these cars are popular, I think they can be a reasonably viable ownership experience. But in places where they are rare, good, knowledgeable people are much less common, too, and competent repairs may be hard to impossible to find.

    I guess you could say that if you want to pretend to be a rich man, it helps to be where there are critical masses of rich men to support repair infrastructure …


  • avatar

    How about retrofitting back to the halogen lights?

  • avatar

    And THIS is why my special-ordered BMW has plain old halogen headlights.

    HID = $1000 answer to a question that did not need asking. They aren’t THAT much better.

  • avatar

    Wow guys $1000 to replace HIDs? DDM tuning has a lifetime warranty on their HID kits, comes with a set of bixenon HIDs of your color temperature choice, ballasts, wiring harness. Costs about $70 USD.
    Pretty cheap if you ask me! I don’t know where ya’ll get the information that HIDs are expensive, they are not. I’ve had this HID kit on my car for over a year now and I have the lights on all the time when I’m driving during the day, works fine. Very bright.

    Bixenon; It has a little motor/solenoid that sucks the bulbs in when you want high beam. It doesn’t use any blockers.

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