ploo

Hey guys, I'd appreciate some help from all you experts out there:

Tonight I started my C320 and pressed the knob to recall seat memory settings. At this point, I started to hear a fairly loud thumping noise coming from the dashboard. I turned off the HVAC and stereo, and listened to it carefully.

The thump sounds like a strong tap on the top of the dashboard (directly over the speedometer, let's say) if you were to tap it with your fingers. It happens every 7 seconds or so, on a rhythm. I just tried to duplicate the noise, and it happened with my key in ignition 2 position (full on) but without the engine running, HVAC off, stereo off.

After a couple minutes, the thumping stopped this last time I tried to duplicate it. My mom (it's her car) is pretty freaked out by the noise and tomorrow we are going to have it towed to the dealership.

Any ideas on what this is? I really don't want to have the car returned to me in a couple days with "could not duplicate."



Any help is GREATLY appreciated! Thanks.
-Phil

ML55CLA45

i have no clue as to what it could be.... but i dont think its anything major, major enough to have the car towed to the dealer.... just drive it to the dealer and if its making the noise on the drive up there.... then you can point it out to your service advisor..

annoying noises suck.... i myself need to get my seats tightened the next time im at the dealer

my two cents-
-carino

1979- 300d
1994- e320
2002- c240

ploo

Good point, but in case it's something related to failing power steering or anything related to the steering...we're gonna have it towed anyway.

As my mother put it quite simply, "Aren't our lives worth more than a towing fee?"

=D


Thanks for your reply.
Phil

Saprissa

I had a VW bug that did that. It turned out to be the little hamster, that runs circles inside a little cage-wheel behind the Speedo, was hungry. I fed him a couple of kibbles and the noise went away.

CitronC230K_03

let mus know what you find out.

OZC32AMG

Hi Phil,

My car is making the exact noise you stated and it started doing it yesterday afternoon?

What did you find the problem to be?

It sounds to me as though an A/C duct is trying to open or close but is sticking and making a knocking noise at it springs back.

Please let me know what you found as it is valuable feedback like this that helps make this an interesting forum.

Thank you,

Joe

MB-BOB

There are vent gates behind the dash that have plastic gears that strip against the HVAC stepper motor. I've had this situation myself, and the dealer replaced several parts in the ductwork under warranty.

ctC230K

could it be your power steering wheel tilt/telescope motor? you said the noise only happened when you pressed the memory button to recall your settings? one of the settings is the steering wheel position.

swale

Sounds Like the A/C Duct

dontwakemeup

Hi MB-Bob,

Do you know how much the warranty work amounted to? I'm experiencing this too but I'm out of my warranty...

Thanks!

OZC32AMG

ctC230K,
No the noise does not occur when pressing the memory setting button. The original poster said that. It occurs when you turn the ignition on. It only occurs on HOT days though. Whick makes me believe that when the A/C has to supply cold air only a flap must have to be diverted which has the stripped stepper motor drive gears.

MB-BOB,
I am out of warranty too and I believe you have described the exact problem. Any idea of cost?

Joe

x-tian-230k

It happened to me a while ago.... Its not a big deal...the dealership will fix it underwarrenty.... They said it had to do something with the air duct...i wasn't paying attention much...but its not big deal...... love warrenties..!

OZC32AMG

For those who have warranty, it's no big deal.

I have been quoted $2000 AUD to have the stepper motor replaced.

To me, that's a big deal!

Mono6

had the same thing happen on my car Any Update on this problem?

trisonics

I am having the same problem since three weeks (funny how everything decides to break down right after you buy the car). It clicks 8 - 10 times before it quite.

A sure way to know if it is the AC duct stepper motor is to change the AC direction from the existing one to, say, diffuser only or foot well area. If you notice that nothing changed by turning the knob, then it is the stepper motor.

My $.02

mleskovar

Do a search on 'stepper motor'.

Mono6

I have found this thread most useful and informative. tnx!!

https://mbworld.org/forums/showthrea...=stepper+motor

southernwake

I had the whumping sound right after I bought the car in August 2010. It was on the drivers side, right under the steering wheel it sounded like. It only lasted a few weeks then stopped. Now the air blows weakly out of the vents, it is cold but you can only feel it blowing if you put your hand close to the vent. Even if I turn the rear A/C off it is still weak. The rear A/C works great. If you let the A/C run for a little bit it does cool thing the car off.

It also sounds like all the air is blowing really hard behind the dash on the passenger side, glove box area. I dont really notice it blowing on my feet though as others have described. I have done the searches and found quite a bit of great info and write ups for DIY. I plan on resolving this soon, but wanted to get some insight. To me it does sound like a stepper motor lever/ stepper motor itself. I would assume it would be the one on the drivers side I am having an issue with but I could have more than one out also? The drivers side and passenger side blow with equal strength , no difference. Could the sound I am hearing from behind the glove box be from the stepper motor issue as well?

Thanks, Andrew