EPineda

Help!! I'm baffled!! This thumping noise started yesterday when I warmed up the car. Sitting inside the car, there is a very, very pronounced thumping noise inside the dashboard once every 5-6 seconds, you can hear the thumping sound and feel it with your hand. I though at first it was the CD changer in the glove compartment, took out the disk cartridge but it was not it. Then, I turned off the radio, checked dash controls to make sure they are all off. For some reason, when I turned ON the wiper switch, the noise stopped, not sure why because the wipers were on OFF position. I thought about the rain sensor that operates the wipers when raining but the wiper switch was definitely on OFF position. Shut down the car, open the hood, restarted the car, the thumping noise was back, check if noise was coming from the engine compartment but could not tell since the engine drowns noise. Turning 'ON' the wiper switch, (for some reason) stops the noise. I'm very baffled.

ontmiss

try this https://mbworld.org/forums/c-class-w...ost-works.html

EPineda

Ontmiss, thank you for your reply on this thread. I followed the link you provided to the Run the HVAC stepper motor resynchronization. If I run the HVAC stepper motor resynchronization, as described in the link, does the engine has to be on or running? Also, the wiper switch as three (3) positions, which would I use? Sorry but this is the first time I've heard of the HVAC stepper motor resynchronization. Appreciate it if you could provide detail steps, if possible. Thanks again!

Without waiting for a response, I tried to run the HVAC stepper motor resunchronization per instructions from link provide by ontmiss, holding down the wiper switch and recirculation button (with the motor running and not) but nothing happens. Repeated for several times, holding down the switch/buttons for more than 30 seconds, but still did not work. Am I doing anything wrong? Any suggestion?

ontmiss

Nothing to do with wiper switch. Hold recirculation and front windshield defrost

ontmiss

more info here https://mbworld.org/forums/c-class-w...imatronic.html

EPineda

Sorry, I misunderstood the instruction on the link you provided. Using the recirc and defrost buttons, I was able to start resynchronization cycles, with the flaps in different open/closed positions. Yes, the airflow that goes down to my feet is NOT working. That could be where the noise is coming from, trying to direct the air and probably stucked closed. With the cold weather coming, I'll need to take cared of this problem soon. From here on, what would be the next step, repair/replace the stepper?? What is the part called? Part Number?? Any link I could check? Suggestion??
Thanks again.

ontmiss

https://mbworld.org/forums/c-class-w...g-hissing.html

EPineda

Ontmiss, 'THANK YOU', Reading the link you've provided, I found in the thread instructions povided by 'Racin_Fool', describing the steps to take in replacing the stepper broken linkage, including the kit PN, etc. Again, you're a life saver and all. Thank you much!!!!!

nrg_mike

Good luck with the replacement. I wanted to do the fix on my 02 coupe but was too lazy to take things apart and figured I'd probably leave some pieces out during the re-install. LMAO.

ontmiss

Good luck and don't be lazy to take some pics and post here

contact148

having done this repair

I can say its very easy take your time and follow the instructions

EPineda

I finally did the work on my 2004 C240 by following the instructions found in this forum. I followed the instructions, took my time in dismantling the floor center console and dash, took me a total of 4-5 hours to complete the whole job. I'm glad to say, I found a cracked stepper motor plastic lever (steeper motor on the driver side. Yes, there are two (2) stepper motors in there), replaced the cracked plastic part, put everything back and done. The HVAC on my car is now quiet and working well. Total cost of the part, $17 for a set of 2 levers. I have a spare part for next time (hopefully there will be no next time). I thank you this forum for the diagnosting the problem, detailed instructions and pictures. I'm glad to say I did not go to the stealership to let them do the job that might have cost me a small fortune. I love this forum!!!!!!

pcy

if you had taken the car to the dealership for repair, including the diagnostics fee, it would've cost you ATLEAST $600.

While you had the dash apart, you should've replaced the plastic lever on the other motor as well, even though it's not yet broken.

EPineda

Thanks! You're right! I pulled the other lever out though, it was still good and the part was different from what I had on hand. If I have to do it again next time, it would be real easy work for me.