I'm looking for assistance with a headlight issue and I'm hoping the collective knowledge base at sUSA would come up with a resolution.

I had two headlights of different ages blow about a month ago at the same time. It happened the day before I was going to the dealer so I picked up some more expensive brighter lamps and had the dealer put them in. I asked them to diagnose what would cause two lamps of dissimilar age to die at the same time. They gave me some bull about it being a coincidence, that both blowing at the same time is rare but no unheard of.

I didn't fully buy it, but figured they're the experts. One month later they both went out again at the same time. I've got an 08 and haven't had any issues until my right lamp went out last winter. At the time I didn't think anything of a 3 year old bulb going. Still don't. However, now that I've had two pairs go in a month, obviously something wrong.

I found your old post about the A 451 540 23 06 resistance kit that limits voltage to the lamps but that sounds like a "patch" as opposed to a repair. Do anyone know of a better fix or is the resistance kit the only option?



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Thanks for the input. We have similar but different issues. My lamps both go out at the same time. The first time they were changed out right away as I had an appointment with the dealer for my 40K service. However, this last time I didn't have time to get the car in and during the wait time both headlamps came back on.

In my case it's not a burnt filament due to overvotage, extra bright lamps, or dirty hands. It do believe it could be a connector, harness, switch, or bad wire. Anyone have a wiring diagram?



You may want to visit and pay for a subscription to that service.  That's your best shot if you want to do your own service. 

You're right, it doesn't seem like a surge.  Could be a loose connection, or a faulty relay or any number of things.  Calling smart direct is always an option.  Even if they haven't heard of the issue, they would be able to work with the dealer to find a fix.  Also, Kamaal suggested a subscription to That's your best bet at getting a diagram or more technical information for your smart.  Best of luck!

Itasca Mark said:


Originally I thought it was a surge but the fuses never blew and the lights came back on. If it was a surge as I originally thought I would think that either the fuse would blow or the light filament would blow out. However, when the both lamps came back on the only thing that was blown was my surge theory.

On another smart site SCOA I chatted with someone who who's very knowledgeable with the car. He thought the issue could be a high voltage creating the problem because older smarts were known to sometimes have that issue. Even though my car was good for three years I thought he was probably correct. Then the lights came back on. If they were blown out due to high voltage, again they would not come back on.

So I'm leaning towards a loose connection. Of course I still could be wrong. Certainly my dealer was incorrect, the first time both lights went out at the same time they simply chalked it up to a grand coincidence. NOT.

It seems like the service I'm getting from the dealer I bought at is slowly getting worse. Luckily, we have another dealer in the area. I'm going to try them if I can't dig up a schematic myself.

Thanks for the input. I do like the idea of calling smart directly. If nothing else they may have heard of this issue and can advise me of a fix. Even if I'm not capable or don't have the right tools, I can let the dealer know what to look for.

All the best,



Kammal & Quinn,

Thanks for the input.

Veganman, I'm sorry you feel the way you do...  but look on the "bright" side.  At least these are the easiest headlights in history to change!

Btw, I too believe vibration has a lot to do with cutting bulb life.  I've gone through a few in my 203,000 mile smart and others...

Veganman said:

I am on my 3rd driver's side low beam bulb in 2 years. The dealership tested everything and said it's just the way it is and blamed vibration. I don't agree but I have a box of bulbs now so I don't have to pay them $39 to replace it each time.

This car loves bulbs..  Strange part is the right one I replace about once a year, the left one I replace every 4-6 months.   I purchased a case of OEM OSRAM bulbs on ebay for about $3 a bulb, well worth the investment.  

There is a headlamp resister kit that you can acquire at your smart Center parts dept. The p/n is: A 451 540 23 06.  This is what smart recommends you install to prevent frequent headlamp bulb replacement. This kit is also mentioned in the 1st post.

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