Retrofit Retrofit
Car: Mercedes-Benz | CLK | W209 | Avantgarde | Coupe
Engine: CDi | 0 | Inline 5 | (170 BHP) | Turbocharged | Diesel

Bi-Xenon retrofit

It is possible to retrofit Xenon's to a W209 CLK, but I would not recommend it for the following reasons.

Reasons to avoid this particular retrofit

Levelling system

Halogen headlamp vehicles use a pneumatic levelling system, why this is I don't know, I suspect it's cost cutting as the parts required to make this work are cheap and simple, and vacuum can be obtained from the inlet manifold and regulated with a simple solenoid. The pneumatic system cannot respond fast enough to auto-level the headlamps on the move therefore, the Bi-Xenon headlamp equipped cars use the more usual electronic stepper motor system. It is not economically viable to retrofit this electronic levelling system.

I am not against the retrofitting of Xenon's without auto-levelling; well adjusted lights do not cause a problem (Xenon systems inside halogen headlights, especially reflector systems, is a different matter entirely!), however another snag with the W203/W209 is that individual cars cannot be guaranteed to work with Xenon's.

Control module

The Mercedes convenience module features a very nice piece of coding which slowly ramps up the supply voltage to Halogen headlights, thus prolonging the life of bulb filaments. HID headlamps require a specific voltage to the ballasts in order to ignite a cold Xenon bulb, and so connecting a Bi-Xenon to a Halogen equipped car will result in strobing as soon as the ignition is switched on.

The solution to this problem is to re-code the convenience module to enable 'Xenon mode' which provides direct +ve to the headlamps, but as I found out, not all cars will accept this coding. My dealer was very helpful and didn't charge me because the car wouldn't accept the coding, but in his words:

"Retrofitting these is very hit-and-miss, we have a lot of cars which don't accept the coding."

Having said all of this, the lights can usually be sold on for what you paid for them, so if you feel like taking the chance then it won't cause your car or wallet any harm should they fail to work.


All HID headlamps for the W209 are Bi-Xenon and are not model year specific. The lights are plug and play however, as Bi-Xenon's use electronic levelling then any kind of levelling other than initial alignment becomes impossible. The existing pneumatic connections must be blanked off.


The headlamps I purchased to try in my car had come from a breakers yard, and the usual case here is damage to the mounting lugs. The actual headlamp covers can be removed by carefully heating up the join and parting with a plastic trim tool once the sealant has become pliable.

The following images show how I repaired the headlamp brackets (as best I could - it's not pretty), I made good these repairs on the inside of the headlamp with Sikaflex 221 sealant.

Update 25/09/2009: I have been informed that Mercedes supply repair brackets for the headlamps.

w209bixenon w209bixenon w209bixenon
© Mark Stewart, Tuesday 25th November 2008
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