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.

  • Steve Biro I don’t bother with dedicated summer or winter tires. I have no place to store them. But the newest all-weather tires (with the three-peak mountain symbol) are remarkably good year-round. The best of them offer 90 percent of the performance of winter tires and still fall mid-pack among summer ultra-high performance tires. That’s more than enough for my location in New Jersey.
  • Carfan94 Never, it doesn’t get cold eneough here in TN, to switch to winter tires. But it gets cold enough that running Summer tires year round is impractical. I’m happy with my All seasons
  • Analoggrotto Anyone who has spent more than 15 minutes around a mustang owner would know this will be in insta-hit.
  • Akear If this is true then they won't go out of business. Good for them!
  • FreedMike Interesting time capsule.
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