Piston Slap: Going Ballast-ic on Bi-Xenons?

Sajeev Mehta
by Sajeev Mehta

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 sajeev@thetruthaboutcars.com . Spare no details and ask for a speedy resolution if you’re in a hurry.

Sajeev Mehta
Sajeev Mehta

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  • Krhodes1 Krhodes1 on Mar 22, 2012

    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.

  • Danwat1234 Danwat1234 on Mar 26, 2012

    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.

  • Luke42 I tried FSD for a month in December 2022 on my Model Y and wasn’t impressed.The building-blocks were amazing but sum of the all of those amazing parts was about as useful as Honda Sensing in terms of reducing the driver’s workload.I have a list of fixes I need to see in Autopilot before I blow another $200 renting FSD. But I will try it for free for a month.I would love it if FSD v12 lived up to the hype and my mind were changed. But I have no reason to believe I might be wrong at this point, based on the reviews I’ve read so far. [shrug]. I’m sure I’ll have more to say about it once I get to test it.
  • FormerFF We bought three new and one used car last year, so we won't be visiting any showrooms this year unless a meteor hits one of them. Sorry to hear that Mini has terminated the manual transmission, a Mini could be a fun car to drive with a stick.It appears that 2025 is going to see a significant decrease in the number of models that can be had with a stick. The used car we bought is a Mk 7 GTI with a six speed manual, and my younger daughter and I are enjoying it quite a lot. We'll be hanging on to it for many years.
  • Oberkanone Where is the value here? Magna is assembling the vehicles. The IP is not novel. Just buy the IP at bankruptcy stage for next to nothing.
  • Jalop1991 what, no Turbo trim?
  • Tassos Jong-iL This would be very suitable in the countryside of North Korea.
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