mis3

When I started my car today (2004 CLK320) at lunch, there was a "click click" coming from the front dash? The noise would go away after 1-2 minutes. I restarted the car and no noise anymore. However, I started the car after work and the noise came back; again it lasted for 1-2 minutes. It sounded like the car was trying to turn over something but it failed.

Just for the fun of it, I tried to reset the temp control unit by pressing and holding both RECIRC and DEFROG buttons together. The indicator lights blinked and they would not stop, also, the clicking noise started and would not stop this time. I had to get off the road and restarted the car.

Other than the clicking noise when I start the car, everything seems OK. Before I bring in my car to scan the code, any idea to what went wrong?

Rudeney

That is most certainly a bad servo motor or linkage in the ventilation damper system. Some of those can be access with a bit of effort (removing dash paneling, center console etc.) Others are "major surgery" requiring removing the evaporator and heater core to pull the entire duct assembly. You won't know until you get a diagnosis to know which is bad.

mis3

Talked to my friend who used to be a MB service advisor.

He said the problem would be the stepper motor (servo), the linkage cracked and hence the noise. The noise appears during HVAC self test when the car is started. He was actually quite sure of this.

I checked the price of this stepper motor: MB parts: $105US, Aftermarket: Behr: $58US.

Does one stepper motor control both sides or there are two?

Eojj

Very helpful post. I've been having this exact issue for weeks now. Couldn't figure what the hell it was lol

mis3

Just got an update from my friend in MB (ex-service advisor, now in sales). He went to the back and talked to a technician. He said the lever kit is broken (2038300033).

These levers (flaps) were changed 4-5 years ago. At that time, the air on the driver side would come out only in the foot area. There was no clicking sound at that time. I remember I did reset the system (RECIRC and DEFROST) and the blinking would stop in 30 seconds.

This time, there is clicking noise and upon reset, the blinking would not stop.

Rudeney

A clicking noise does not always mean a broken lever. A bad servo that cannot report its proper position can also cause this. The driver side floor damper did this on my C240. The servo would just keep rotating after the damper was closed so you'd hear the plastic lever "click" over and over. I removed the servo (only required removal of center console and lower dash paneling to access) and manually rotated it several revolutions. This likely dislodged some corrosion that was preventing its internal contacts from registering its position. After re-installing it and a re-sync of the system, all is well.

mis3

I discussed this with my friend and the MB tech and they both insist that the culprit is the lever set. They ruled out the stepper motor because they said it is quite durable.

mis3

Rudeney: Did you change the servo after all? If no, that servo does last a long time. I have to decide if I change the servo at the same time when replacing the levers.

Rudeney

I would not bet that it's a broken linkage until you pull it out to check. Like I said, mine was the servo - the linkage was just fine. And no, I did not replace the servo. I simply removed it, then rotated it several revolutions by hand, and replaced it. It now works just fine.

mis3

I like to confirm the parts name.

By linkage, do you mean the linkage kit (2038300032) or the lever kit (2038300033)?

Also, is there one or two servo motors behind the center console?

Rudeney

A2038300032 is a kit with all the linkage parts, but not the actual "operating lever" which is the flap itself. Replacing the flap requires removing the entire duct (a major job).

A2038201642 is the "stepper motor" or servo that drive the linkage that operates the flap. If you have the "full dual" climate control where both sides can set separate vent outputs (not just separate temps), then have 10 of these servos and ten linkages and ten flaps. If you have the standard climate control with separate temp controls but shared vent control, then you have six of them.

When you have a problem, it's best to get a scan of the ACC to know which one(s) are causing the problem. They all share the same servo and linkage, but there are different "flaps" or "levers".

Eojj

Mis3 did you figure out what the issue was? If yes, what did you fix and how big of a PITA was is it to do it yourself? I saw a few DIY's on the w203 forum and it looks like a headache. The 1-2mins of clicking annoys the living hell out of me every morning but I'm trying to ride it out as long as possible before I have to pull the panels apart

mis3

My friend (ex service advisor) and the MB tech are adamant that a broken flap (lever, 2038300032) is responsible to the noise. The tech will replace it for me in the coming weekend of Jul-1.

I asked maybe the stepper motor failed and he said that the clicking noise was the motor trying to turn the lever. According to them, this showed that the motor was working.

I will report back after the activity.

mis3

When the MB tech opened the dash and console, it found out one of the flaps was broken. He also saw that the stepper motor was in bad shape. He recommended to replace it as well since the dash was opened.