sandra1

I know this has been covered but to no avail did I find anything. Here's the issue. When the headlights are turned on only my drivers side comes on on this 2002 ml and I hear a clicking sound for about two seconds then it shuts off. I swapped the bulb and ignighter from the drivers side to the right and both are fine, so that's not the issue. I checked for voltage on the left side and found the green wire coming in was supplying power to the headlight, all others had no power. Someone mentioned a relay in the headlight assembly but never elaborated on what it does. Any help to get this light back up and working would be great.

Maj. Dundee

Are they original equipment Xenon or did you or someone else make them Xenon?

Try swapping the entire headlamp and see what happens.

sandra1

What will that solve? Come on, yu have more than that for advice.

Maj. Dundee

You are exactly correct. So my additional advice is solve it yourself.

sandra1

Your response is totally beside me, Maj. what? were you actually military at one time cause if you were, pity on you. Been retired AF for many years and can't get around like I use to with my injuries and you spit on me, figure it out to a fellow vet is not a good answer for me.

art_arev

Swapping headlights will tell you if you have a problem with the wiring or the headlight. If the working headlight will work in the passenger side then most probably your ballast is cooked because you said the igniter & bulb are ok. Swapping headlights in your case is the key to correctly pinpointing the problem.

sandra1

Art,


Where is the ballast located, cause there is a clicking or ticking sound when it does not light up for a few seconds.

art_arev

Ballast is attached to the headlight. Its a silver box on the bottom/underneat of the headlight.
The ticking sound is from the igniter.
But, I would follow Maj.Dundee's advice first & exchange the headlighs to find out if its a wiring problem or a headlight component problem.

sandra1

Will do Art, and post results.

sandra1

Did the swap and the headlight from the left works on the right side. So it's the ballast Art that I need?

art_arev

This means there is no problem with the wiring. It is a Headlight component problem. To be 1000% sure that the bulb & igniter from the right headlight are ok do this: replace the bulb from the non working Headlight into the working one. Next do the same with the igniter. If in both instances the Headlight works then you have a faulty ballast. Of course you have to do this while your left (working) Headlight is plugged into the right side.

sandra1

I did that at the beginning and the bulb and ignighter worked fine on the left side

art_arev

So there is only 1 component left, which is the ballast. The part # is on it. Get a second hand unit. Brand new ones are very expensive.

Jimbo Bigbelly

Thanks, Sandra. I understand. Ranger, tunnel rat, and silver star from the shootout at the embassy. Some of me doesn't work very well anymore either. Still carrying some extra lead.

Being old and um stoopid, I can't get the terminology so I'm not sure what to check. If you can help it would be great. I have the HID factory package on my ML500. It's my driver's side that has the problem. No light.

I bought new bulbs and put them in (both low beam HIDs and high beam halogens). No change, same symptom.

There is a black potted block at the back of the HID bulb. I swapped that left for right, and no change in symptom. I'm not sure if you call that "igniter" or "ballast". I would call that "ballast".

There is a black plastic wart (sorry, I can't describe it any other way because I don't have enough smarts) at the back of the headlamp module which holds both high and low beam bulbs, that clicks when I turn on the headlights. It clicks 10 times. The click is very loud, and I assume it's a relay. Now get this: when I turn on the headlights with the bright-dim switch in the "bright" position, the bright beam on my failing HID side blinks with the click. 10 times.

If you call the block at the back of the HID bulb the "ballast" then I can't find the "igniter" unless it's inside that wart that clicks when I turn on the headlights. But frankly, I believe that's just a relay.

Now to raise yet another terminology issue, I went to a 3rd party mercedes repair shop today and we looked at the wiring diagrams. Their terminology isn't anything like we're talking about here, in their schematics the light switch on the steering column goes through 2 "activity monitors" then to the headlight. But it's unclear where the power comes from, since the switch on the steering column cannot supply enough power for the 55 watt HID bulbs. We could not find a fuse that would supply power to the headlamp. We could find it for the bright lamps, but not the HID low beams.

I cannot find a silver box around my headlamp housing anywhere. I see the power wires coming in, and I see a separate connector which I believe to be sensor wires since when I hook up my meter they have 0 volts on every pin. But no silver box. I see the headlamp housing, with the wart that clicks. Inside the headlamp housing under a cover I find the HID ballast and under that, the HID bulb held in by a couple of spring clips. Also inside the headlamp housing, under a separate cover, I see the halogen bright bulb.

Can you help me find either the "ballast" or the "igniter" which seems critical to fix the problem? Thanks!

art_arev

Jimbo, the black small box behind the bulb is the IGNITER. Be careful handling them. If you break the small clips/legs they become useless. The clicks you are hearing is the igniter.The ballast will only be seen if you remove the headlight. It is attached at the bottom of the headlight. The HID XENON low beams don't have fuses. In your car the power to the low beams goes from the combination switch to the AAM. From AAM a reference low voltage comes to EAM. EAM sends voltage to HID XENON low beams.
Follow what Sandra did & by method of elimination find out which component is faulty.
Generally be very careful. There is very high voltage in the XENON HID's.
That is the igniter in the picture. The second picture is an igniter with broken attaching clips. The third picture has the headlight resting on its lens. The silver box is the ballast. Disregard the red circle.

sandra1

Thanks Art gone my ballast delivered this morning and got both eyes now. I sincerely appreciate your help.

art_arev

You are very welcome. Glad you sorted it out.

Jimbo Bigbelly

Thanks, Art. I couldn't find the igniter control module because it was mounted under the plastic headlight housing. Before I saw your post, I went to an aftermarket Mercedes repair guy who showed me the access nuts under the fascia coverplate at the bottom of the front of the headlamp module (and how to squeeze it to get that cover plate off) and the one extremely long bolt at the top of the housing. Once those are removed, the headlamp module comes right out and the 3 plugs can be unplugged. In 45 minutes I had removed both housings and swapped the ICMs, and Lo! you were right. The ICM has a Hella logo on it, and when I went to the dealer to get another, they wanted $745 US for the replacement. I ordered from Amazon what they call the " Mercedes (03-06) Xenon Headlamp Control Unit LT or RT" for $199. It came from one of Amazon's suppliers in 2 days, and another 15 minutes it was in and I was lit up!

Thanks for the help!

I don't know if this link will stay active but here's the link to amazon:


PS I cracked open my failed ICM and found that the transistor that drives the coil is bad. I don't see any overvoltage protection diodes on the collector of that transistor, so I suspect this failed over time because of the high off voltage from the coil presented to the collector of that transistor when the transistor is switched off. (That ICM is a pretty simple switching power supply). Bottom line, I think buying a used unit is probably not a good idea because that transistor is probably going to fail sooner or later. A new one or one with very little use will last much longer. I'm gonna get another transistor and change this one out, and add a UES1302 switching diode to the 12V rail and I think for 4U$D I'll have a spare 745U$D (robbery!) unit.

PPS: removing the headlamp module really makes the changing of the bulbs easy! And no fear of breaking off those tabs like you mentioned!

art_arev

Well done Jimbo. Glad to be of help.

Please let us know if after change of the transistor ,the ballast did work.

sandra1

Next to the HID headlight assembly is a halogen light also to aid according to the manual as a high beam. Before I changed the ballast on the right side, when I clicked to high beam that separate 50 watt light would be the only one on that side that would light up. Thinking the left side probably had a burnt out bulb I ordered a new bulb set as neither one would light up after the ballast change, which shouldn't have affected that light anyway. After new bulb install I still don't get the separate halogen bulbs to light up. Any ideas where to look for this issue? I haven't checked the fuse box after the first time and both fuses looked good at that time. Not sure if those separate headlight fuses on the passenger fuse box are for which lights.


Thanks for ideas.

Jimbo Bigbelly

Hi, Sandra
I guess by your post, you got both low-beam HIDs working now.

The 2 high beam bulbs (H7's) next to the low beam HID bulbs are powered from the fusebox in the passenger footwell. They are 7 amp fuses. It's unlikely both are bad.

Right next to the 2 high-beam fuses is a control relay. I don't have access to my vehicle right now, but I think it was T5. You can pop that out and check the coil resistance (should not be an open circuit). If you pull one of the fuses you can plug a "spade lug" into the side closest to the relay, and you should measure 12V there when the bright switch is on. You used to be able to buy these lugs at Radio Shack, but since they're going OOB, maybe not anymore. You can break apart a fuse and remove the plastic, and use that to plug into the fuseholder as well.

If there is no voltage at the fuse, your relay could be bad or the switch on the steering column is bad, or a bad wire in between. To check the relay, you should hear a "click" when you toggle the bright/dim switch on the steering column. (Radio off :-)> ) And you should measure 0V in the dim position when you're plugged into the fuse side closest to the relay, and read 12V when you toggle the switch on the steering column forward. It's easier to do with 2 people. Remember the side of the fuse that's "hot" is the side closest to the relay.

Jimbo Bigbelly

HI, Art

I found out which transistors are bad, but got stuck. I no longer have my surface mount soldering hoods and heat gun, had to sell it in the move to Singapore, and I haven't found anybody to loan me one or who can do surface mount rework.

So I guess for me the only answer is to dump my old one and buy another $200 spare. I don't want used because I believe these are ticking time bombs. It seems they're used in a lot of cars, including Chryslers.

sandra1

What I don't understand is why did one side work before the ballast replacement and now neither work. When the car get's home I'll take a look but I do know both fuses are good.

Jimbo Bigbelly

When you have one low-beam bulb out, and you switch on the bright beams from the steering column, the only bright beam that lites up is on the same side as the burned-out low beam bulb.

This is done through some control logic in the headlamp module.

a guess: it is illegal to drive after dusk and before dawn without lites at all 4 corners of your car; front and rear. Since MB knows it's hard to get these stupid HID systems to work, I believe they did this control logic to let you drive at night with one HID bulb out.

I didn't test to see if the H7 bright beam still lit up when I pulled the fuse and had one HID lamp out. I'm not sure if this "work-around" power comes from those fuses, or perhaps comes from say that Igniter Control Module we both swapped. Someone with a service manual and/or wiring diagram will have to let us know.

Anyway, if you have power at the fuse when the bright beam's on from the steering column switch, then you'll know the trouble is in the headlamp module. Otherwise you need to test the footwell fusebox relay, or the bright/dim switch. I hope it's not your steering column switch because that's really painful to access and you might get a facefull of airbag. Be careful there.

Also, contrary to other posts, there is a relay in the headlamp module. It is inside that wart-like protrusion at the back of the module. You have to pull the module to open it up and check that relay.

Jimbo Bigbelly

Also you'll notice your ICM has 5 power pins and one little skinny pin which is not likely power but is more likely a sense pin. Anyway, there's too many power pins for +12VDC, Ground, +1100VDC, 85VAC. I wonder what that extra power pin is used for: maybe going to that relay to power the H7 brite bulb? Anyway, if the ICM controls only the HID bulb, you only need 3 wires. Interesting to note that the igniter (the block that mounts on the back of the HID bulb) has 3 wires. I suspect the 3rd wire is the sense wire that goes back to the ICM (that one skinny pin) to tell the ICM that the HID bulb is not functioning, and the ICM then controls the power to the bright bulb. This is just a guess, but it's the way I would have designed it if I wanted to power the brite bulb when the HID bulb is not functioning.

I was never able to find the fuse for the ICM. It's not inside the metal case, which wouldn't protect the power wire going to the ICM. I wonder where it is.....

I never learned to buy the service manual for something that was expensive to fix, like a car, dishwasher, washer/dryer. I should have learned by now.