xenon headlamp issue - n/s works o/s failed

[cikko]

Hi All,

I bought a lovely 2005 W211 E320cdi a while ago and due to family reasons, had to store it for a few months without using it.

Now I want to use it and have a faulty o/s xenon headlamp (low/dip beam). The nearside is fine.

I changed the bulb to no avail and then changed the balast over - so I have proved the ballast and bulb are OK.

On the main 4 way connector on the back of the unit, there is a brown (ground) and yellow/black wire - which both o/s and n/s have 11.19v (battery voltage is 12.95v). White measures (I beleive is power for main beam or something - maybe the auto aim adjust???) and then n/s is a black with green stripe (measures 0.017v) and o/s has Grey with blackstripe and measures 11.19v. All these voltages change when plugged in or unplugged....

It's very confusing!

I thought it could be a relay or something to do with CANBus but what?

I disconnected all relays one at a time (next to o/s suspension strut and adjactent the ecu) - but the n/s xenon stayed on... so not relay controlled!

So - with the voltages being the same on both sides - surely the wiring can't be at fault. If no relay and all fuses are intact, can't be that. I suspect:

1) Headlamp unit somehow broken and needs to be removed - front bumper off jobbie arghhhhh

OR

2) I read here about a buy in April who had an accident damaged e320 and he had read "somewhere" that a downgrade from xenon to halogen had to be updated to ecu. He has o/s failure like me... but mine is ONLY the low beam - everything else is fine!

I wonder if someone has altered my car in some fashion.

Before I remove bumper - does this sound like a recode for ecu or something?

If someone can help me I'd REALLY appreciate it!

Stu :bannana:

 

[lexman8]

Did you check/change the igniter?

 

[bob6600]

and then changed the balast over - so I have proved the ballast and bulb are OK.



Stu :bannana:

Did you check/change the igniter?

Looks like he tried that already

 

[Starky]

How's the battery?

 

[lexman8]

Looks like he tried that already

On my car the ballast and igniter are separate. The igniter forms part of the base connector for the bulb whereas the ballast is attached underneath the headlamp assembly.

 

[lexman8]

All the voltage readings given by the OP are below 12v.

An HID bulb requires several thousand volts from the igniter to strike the initial arc then ~80v from the ballast to maintain it. Note that these are potentially dangerous voltages. I don't know if you can easily measure these voltages since the ECU may switch the circuit off if it detects a component failure.

Also, the ECU does need to be set (via STAR) to whichever headlamp type is fitted. However, I think this is only so that the bulb failure warning operates correctly as HIDs draw a smaller current than standard halogens.

 

[bob6600]

On my car the ballast and igniter are separate. The igniter forms part of the base connector for the bulb whereas the ballast is attached underneath the headlamp assembly.

My mistake, I stand corrected

 

[cikko]

Thanks for your thoughts so far

The battery is OK as I kept it charged up.

I'm foxed as I don't know what needs to happen to make a xenon bulb light up.

In my research - another MB forum in the USA, someone had a later facelift style headlamp unit and bench tested it. To get it to work, he needed to power and earth the bulb AND the CANBus, as power to bulb alone was not enough. Now I have no idea which connector deals with CAN.

This makes me think that the bulb is permanantely powered and only illuminates when a CAN signal is given to the ballast. The ballast connector has 4 (I think) very small single core-ish feel plastic coated wires, which auto disconnect when you rotate the ballast for removal....

Something that may hep with diagnosis - this bulb failure was seen at MOT station and when the dip beam is on, the n/s obviously works, o/s no light at all. BUT when main beam is on, the o/s reflector goes "black" internally - as though the power was on to the bulb - but it's just not emiting light??? It's really weird....

My own thoughts are that I either need to go through the pain of bumper off, headlamp out and see if I can see failures OR if there's something "magical" happening that STAR would see???

Please help!!!

argghhhhhh

 

[lexman8]

First thing to say is that your car's HIDs seem different to mine but the post on the US forum may not accurately describe what's going on. Whatever the car, the CAN bus only ever connects to an ECU and it is the ECU that interprets the digital data and then controls whatever is connected.

The attached pic shows the HID on my CL. The bulb base is visible in the centre of the opening with the igniter (which clips on to the base of the bulb) lying off to the left with 2 thick grey wires going into it from the ballast. The ballast cannot be seen as it is hidden on the underside of the headlamp unit. The thin white and brown wires are to flick the metal shade that selects between dip and main beam on bi-xenons.

It's possible that the ballast and igniter are one unit rather than being separate as on my car. Have you checked this?

 

[cikko]

lexman - thank you...

I may be confusing the issue here with incorrect use of terminology... the buld is a d2s like yours and protrudes just like yours. The unit that sits on the base of the bulb of mine has 4 small green wires going to it and 4 plastic lugs that locate into the back of the headlamp unit. The unit that clips in has 2 slip rings - to provide power I guess to the bulb once correctly aligned. I thought the unit that clipped in (different to your CL is what I was calling ballast. But you call it igniter...so maybe I've been falling foul of jargon).

It is interesting that the bi-xenon facility is the flick of reflector - which is working (as in the MOT bay I could clearly see the bulbous parts of the projector headlamp shape was silvery until main beam with selected and then the "eye" went black...so a reflector is working in the background. That's good to know.

Tonight I've been searching for bumper mountings etc and will attempt a headlamp removal tomorrow. This will at least help me diagnose further and see what those units are on the underside of the headlamp.

Fingers crossed I find corroded terminals everywhere underneath!!!!! It may be a PITA but it will be fixed with my soldering iron!

thank you for your help