Go Back  MBWorld.org Forums > Mercedes-Benz Sedans > C-Class (W203)
Hissing noise/no air from dash vents >

Hissing noise/no air from dash vents

C-Class (W203) 2001-2007, C160, C180, C200, C220, C230, C240, C270, C280, C300, C320, C230K, C350, Coupe

Hissing noise/no air from dash vents

Old 07-09-2019, 02:29 PM
Thread Starter
Join Date: Apr 2019
Posts: 3
Likes: 0
Received 0 Likes on 0 Posts
2002 Mercedes c240
Thumbs down Hissing noise/no air from dash vents

Hello everyone,

Since the stickied thread on this subject has seen one post over the last two years, I'm making a new one. Maybe the mods can sticky this thread and give the subject new life.

Anyway, I have a malfunctioning vent system on my 2002 C240. I can not get air from the dash vents (the ones directly facing the driver/passenger seats). This inoperable state is accompanied by a hissing noise for several seconds when trying to change the direction of the airflow. I understand the sound can be coming from the vacuum lines that control the directional vanes. My question is: where are these lines located and what is the best way to get at them for inspection/repair? Do I need to pull the whole dash off in order to access the lines effectively? The previous owner of the vehicle blamed one of the stepper motors for the issue, but I'm starting with the simple/inexpensive things first.

Any input on this subject is appreciated.

Thank you
Dollard02c240 is offline  
Old 07-12-2019, 06:20 AM
MBWorld Fanatic!
slammer111's Avatar
Join Date: Dec 2003
Location: Vancouver, BC, Canada
Posts: 1,851
Likes: 0
Received 25 Likes on 25 Posts
2003 C230K Coupe Orion Blue
A W203 doesn't have vacuum lines. The HVAC dampers are all controlled by electronic stepper motors. Your C240 has 6 of them spread throughout the interior under the dash, behind the instrument cluster, radio, and glove box.

Not sure why you had to start a new thread, as the information would be unchanged from before. You either need to re-synchronize the HVAC system, or replace any motors that died (doesn't look like the case in your situation). The stickied thread probably has what you're looking for. What you're describing is a very common W203 (and whichever other models use the same stepper motors) problem.

With that said, these stepper motors are known to fail when the gears wear out and teeth break off. It's always a fun time ripping out the entire dash area. One of the most difficult (time consuming) repairs for the W203. I still have nightmares over this.

Last edited by slammer111; 07-12-2019 at 06:23 AM.
slammer111 is offline  

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

Thread Tools
Search this Thread
Rate This Thread
Rate This Thread:
You have already rated this thread Rating: Thread Rating: 0 votes,  average.

Quick Reply: Hissing noise/no air from dash vents

Contact Us - About Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
  • Ask a Question
    Get answers from community experts
Question Title:
Your question will be posted in: