Hello, everyone. This is my first thread in this board.

I own a W203 C220 CDI (Europe).

Recently, I've started to hear the infamous "click of doom". (Lasts around 1 minute after turning ignition on, clicks spaced apart 1 second).

I have tried a reset (defrost+recirculation). This will run indefinitely, together with the clicks.

I have removed the cover of the driver (left) foot well and I can see where the noise comes from.

However:

- Flap seems to open and close properly in response to the stepper motor's movement (when closed, I see it "vibrating" to the clicks, which suggests the noise is coming from here, but the arm itself seems still, which is rather odd);
- The plastic lever is intact.

I have created a video showing the description above, uploaded here:
Can someone help me figuring out where the issue is?

Thank you!

 

You're looking at the wrong motor. There are 3 in the vicinity.

See this post. The motor in your video is M2/6. The one that most likely broke is M2/15, which is actually behind the radio. If you're lucky, the motor is fine but the linkage snapped. The PN for the updated beefier linkage arms is A203-830-00-33. The original thinner arms have a 100% failure rate. See this post.

While you're at it, read the entire thread. There are instructions on how to get to the motor.

 

Hey, thanks a lot for your input.

What puzzled me at first was that, if you see the video, the flap actually vibrates at precisely the beat of the clicks. Maybe it's just vibration coming from the motor above.

Thanks for the post. I'm already familiar with removing all the central dash, as I replaced the radio and the console under it twice by now. I guess I'll have to do that again, and go even further. What a nightmare waiting for me...

 

One extra question, is there any way to have some kind of visibility to the motor, not with the goal of replacing it, but just to confirm visually what the issue is, so I can buy the parts in advance?

 

Sadly no. With that said, the other linkage pieces aren't known for failing. I can pretty much guarantee it's at the M2/15 arm.

In terms of failing motors, I've had M2/15 (broken gear tooth), M2/16 (broken gear tooth), and M2/21 (broken electronic stepper) fail in that order. All 3 of them control the dampers to the various vents. Guessing this application stresses the motors a bit too much.

Just wait until you have to deal with M2/16. That one is a nightmare, as the upper dash has to be removed too. The good news is that once you can reach that one, you can also reach the other 5 quite easily.

 

Yeah, let's just hope you are right!

Let me make you another question, if you'd allow me:

I've seen in another thread, some users saying that the interval between the clicks could indicate if it was the motor or the arm. Do you agree with this and, from my video, does it help in understanding where it comes from?

I forgot to say that everything seems to be working properly! Hot, cold, air going up, down. Clearly there must be a limitation somewhere, it's just that it's obvious it would not matter much for my daily use cases. I don't even drive on a daily basis. I only wish I could have a way to just disable the flap and leave it as it is, even if broken.

 

The arms are guaranteed to fail. The original arms are too thin. Even if they're not broken, replace both.

The thumping noise is caused by a broken gear inside the motor. There are 2 white gears and a black one. When the black one broke (worn teeth) on mine, it created the thumping noise 1s apart as the teeth skipped.

Check to see if the air to your feet can be controlled. For example, when the dial is turned to blow on your face, there should be nothing coming out of the defroster or leg vents. If the air either stays on or off regardless of dial direction, the corresponding motor needs to be replaced. There are 2 motors in the vicinity. One controls the air to the legs, and the other controls the air to the face. So far everyone (myself included) seems to experience the leg air failure first. My face air motor failed several years later.

 

I could finally read fault codes using a Texa OBD2 reader:

B15A8 - flap motor legs area - mechanical fault

More info I found online: B15A8: M2/15 Left and right footwell actuator s or b

M2/15 confirmed, it seems. I dont know what s or b are. Guess I also cant know if issue is the motor or the arm.

 

One extra question:

By "Both", you mean M2/15 and M2/21, right?

 

Nope. Actually for our cars, there is only 1 motor for the legs (M2/15). Only the cars with the digital dual zone configuration will have separate motors for the driver's and passenger's legs. My bad.

If you look carefully at the diagram above, you'll see there is actually room for 2 more motors to the R of M2/21. These can be retrofitted, as well as 2 more motors - defrost above M2/7, and one for the carbon filter (not shown), for a total of 10 motors instead of 6. With that said, it's not really worth the retrofit, as the proper job requires a digital panel, different daisy chain cable, then some other random bits such as a sun sensor, and some other (humidity I think?) sensor. The digital panel is a nice cosmetic upgrade, and can be retrofitted. However, only the driver's side direction dial works because of the missing motors.

The reinforced arm kit contains 2 arms (for the L and R sides), but for the base configuration you'll only need the L piece. The pieces are slightly different and are marked L and R respectively. I am not sure if the L arm can be purchased separately. In any case, it's just a few bucks.

 

@slammer111 you are a beast! Give me a ping if you ever come to Portugal so I can buy you a beer.

I will keep this thread updated.

I have a good relation with the Mercedes reseller here, I will ask the guy if I can take the arms and the motor, and eventually return the motor if only the arm is at fault. Another is option is to go ahead and replace the motor and the arm regardless.

EDIT: Just seen the prices at Mercedes for the motor. Nevermind what I said, I'll find it somewhere else.

 

No worries. Glad to help a fellow member.

Let me know if you find a new motor (PN A203-820-16-42) anywhere outside of the dealership network. The usual sources I look at are all sold out (discontinued).

 

Hello!

Some news. I got a new aftermarket plastic arm for 10 EUR and I bought a used genuine motor for 25 EUR with a build date of 2017.

Im ready for the repair but unfortunately I have found two extra clicks which I dont know if are related to the motor #15 or not.

The clicks seem to be from both the left and right side of #15 and follow a pattern of AB, AB... BA, BA...

I made another video:


However the thing is that no new fault codes appear. It still exists only one (#15).

Kind of conflicted on what to do.

 

Open everything up and replace M2/15. Plug in the climate control cables (just enough to get everything working), then turn the key to position 2, resync everything (hold the defrost and recirculation buttons until they start flashing), wait until the lights stop flashing, then turn the engine off and wait 2 minutes. Turn the key back to position 2 and see if anything else is clicking.

It's possible but unlikely that another motor happened to fail at the same time. Once you have everything opened up, it's very easy to find the problem(s).

 

Thanks.

Yes, I guess that's my action plan. You see, I'd like to have everything prepared in advanced, so I'm not left in a position where I need to replace something else but I don't have the parts. However, if the OBD2 scan is not finding new faults, I do agree that your proposed action plan is the way forward.

 

Hello, @slammer111 the legend himself.

OK, so the job here is done. It took me yesterday, the entire day. I did it calmly, no rush. My father is an auto mechanic, and if there's one thing he thought me throughout the years is that these are the kind of services that you have to do it CALMLY. Take 1 or 2 days for it. Yes you can rush it into 5~6 hours, but chances are you will lose your patience and start forcing things around, and break something. Working in the internal linings of a car is absolutely nerve wracking, at least for me. So I took the day, and took the car to my old man's garage to do it with lots of space and tools.

And, as I said above, I did it calmly, took regular breaks, and had a good lunch with a good glass of wine with my old folks.

About the repair itself:

The arm was fine (I still replaced it with an aftermarket one from AUTODOC). The stepper motor was the culprit.

So I took it out. Then, I had two stepper motors in my hands. The old one from 2003, and the "new" used one from 2017.

I opened both, to see what was going on. The newer one was much better lubricated, compared to the old one, which was mostly dry. The wheel in the old one had some dents missing, leading to the issue.

I took ALL wheels out, from both, to pick the better looking ones. One of the black wheels (not really sure if from the old or newer motor) was also having some smaller dents worn out, so I've picked the other one.





Regarding the motor's body and electronics, I used the one from 2017.

Everything is working properly now. The HVAC test now runs and finishes properly. I've also cleaned up the OBD2 errors in memory. Even those extra clicks are gone.

But this is kind of an ungrateful job, and here's why. You have several options:

1. Buying a new stepper motor from Mercedes... spending almost 300 EUR;
2. Buying a new stepper motor from aftermarket. You have no idea how good are the electronics and the plastics used in them;
3. Buying a used stepper motor. Even if it's a newer one, like mine from 2017, you still don't know how good is the state of the wheels and the electronics, just by looking at them;
4. Repairing the stepper motor with a kit of new wheels. These kits are aftermarket, so same issue of 2.

So assuming you do not buy a new stepper motor, you are never really sure how long will the repair gonna last.

Let's see.

Additionally, I now have the old 2003 broken stepper motor in my hands. I am going to buy a repair kit and repair it, and store it as a replacement for future occurrences.

Thanks once again for your help.

Refs used in this repair:
Stepper motor: A2038201642
Linkage: A2038300033

PS: Feel free to merge this thread with the main one about this same issue.

 

Glad to see everything got fixed. Glad to see you decided to take the DIY plunge instead of just throwing money at the dealership. This repair is among the more difficult ones for the cabin, so now you'll be somewhat ready when the next motor fails.

For our cars, the defrost motor is by far the toughest one as it requires the removal of the upper dash, as well as the trim on both sides of the car. To be honest though, the job isn't actaully too difficult - the intimidating part is the high number of fasteners involved. The only trick is to stay organized. Personally I use a small bin/tray with many tiny compartments, and take photos as I remove each set of fasteners. Then I just look at the photos in reverse order and everything goes back together perfectly.

On that note, be glad you don't have the factory dual zone option. The carbon air filter motor requires removing the entire box or something crazy, as the motor is right against the firewall.