Noisy Air Conditioner ?? Stepper Motor Replacement / Clicking & Hissing
Any idea what is the hissing sound coming from the center vents? Here is a video of the same sound from some BMW driver: (Cant give own video yet)
E46 A/C Hissing Sound - YouTube
My stepper motors are fine and also tried another blower. Core evaporator changed 2 years ago. The AC worked last summer, but could it still need refilling? Can not test AC now since its +5 outside but the hissing sound is making me nuts. It keeps hissing no matter what temp or position the knobs are.

Now here's my dilemma...... The plastic lever arm was good. I didnt have to replace it since it was the upgraded version. But the stepper motor was shot. I took it apart and saw that some of the teeth on the gear were gone. I replaced the motor and when I plugged it all back in and go to resync the motor doesnt move. All the other motors move around. I pushed it a little and it doesnt budge. And after about 30 seconds the a/c control stops resyncing. I still get a little air on the footwell but not like before. So I dont know if its working or not? What do you guys think? Should I go back in there and replace the motor or do something else or go to my mechanic and ask him to hook it up to his computer?
Thanks everyone!
Last edited by Benzomatic76; May 3, 2015 at 11:15 PM.
I forgot to mention, that brace that the motor hids behind is a royal PITA!! Its so hard to move the motor around. If I have to get in there again I just might sawzall that brace out and then just reattach it with some metal brackets and self drilling screws.
The AC system is all plastic. Don' be afraid to move/bend things to get better access to connectors.
The Best of Mercedes & AMG
The AC system is all plastic. Don' be afraid to move/bend things to get better access to connectors.
Thanks!
http://www.ecstuning.com/Mercedes_Benz-2005-C240-203.081-4Matic-Sedan-V6_2.6L_112.916/Search/SiteSearch/2038300033/
http://www.ecstuning.com/Mercedes_Benz-2005-C240-203.081-4Matic-Sedan-V6_2.6L_112.916/Search/SiteSearch/2038300033/
http://www.ecstuning.com/Mercedes_Be...ch/2038300033/
Thank you for posting a link to our site!
David
Ant
I have an odd noise that may or may not be related to the steppers and arms. The car is a 2005 C240 4matic Wagon, post facelift. When I sync the steppers I feel air everywhere it is supposed to be (although it seems to take a long time to switch from dash front to dash top, normal?).
The noise I have is a little tic tic tic that is constant when the blower motor is between 2 and 3.5. It also makes the noise when in auto mode and the fan is blowing at a low speed. Under braking the noise goes away, under acceleration it gets a little louder. It does not eem to change speed with the blower fan and it does not stop after 3,4 or 8 minutes - it will do it all day. It is a light tic, not a loud snap.
I pulled the cabin air filter out (under the hood) and ran the fan at all speeds but couldn't hear any noise there. It seems to me it might be related to a flapper door since it changes with the attitude of the car but since it passes the sync test - and all the air goes where it is supposed to go - I can't imagine it's a broken linkage.
I'm thinking I'll pull the motor out and see if there is anything in there, debris or something, that could be getting into the fan. Anyone else have thoughts? Seen it?
Thanks,
Firstly let me say thanks for the great instructions on how to find these.
Job #1:
This one next to the steering wheel (UK RHD car) didn't have a broken arm, the motor itself was ticking:
So opening up the motor:
... revealed a few teeth on the white gear had worn away.
This particular vent flap only requires a very small travel to do its job (stepper moves through about 1/3 of a complete circle), so removing and rotating the white gear such that the worn-out part sits at the other side fixes the problem!
This short range of movement is specific to the vent flap previously pictured. Others move a lot further, but you could try it out anyway.
Reassembly. The larger black and white gears seen before stay in place (note the worn side of the white gear is now at the opposite end). Add the spring under where the smallest white gear is shown, then pushing down on the smallest gear add the remaining white gear on top. There's a few pins in the lid you need to line up, the most fiddly being the one that centres the smallest gear:
So now your motor is back in one piece with the worn-out section away from contact, set it up on the car with the vent in its half-open position. This ensures those broken teeth never come back into contact with the rest of the mech.
Give it a go - it worked for me!!!

Job #2:
So the other problem sat behind the radio. It was ticking but neither the external nor the internal gears were damaged - odd!
It turns out the external gears had previously skipped one tooth, meaning the specific large-tooth and associated notch were no longer aligned.
I didn't get any pics of this, so in more detail: the car-side gear has one tooth larger than the rest. On the motor-side gear there's an associated cut-out to accommodate this large tooth. If the mech isn't lined up then the large tooth is forced to roll over a non-notched section, forcing everything to flex and resulting in a 'thump' as the highest part of the tooth is cleared.
Remove the motor and realign the large-tooth and notch to cure the issue.
Remember to re-sync with the Recirc+Defrost combo!
Last edited by albad; May 22, 2015 at 11:36 AM.

Strange your other vent rod and gears were misaligned....I wonder if that motor was previously changed and whoever put it in didn't align them properly.

Anyhow good looking out and making this your first post just to share with everyone!
Socket are like common hex socket
Inverted Torx socket starts with E (instead of T as in T35)
Once you figure out you need T35 shape,.... you should figure out length as in common little bit that are interchangeable or do you need longer as in on a screwdriver
Anyways, if your going to work on your Mercedes,... you should have a set of torx screwdrivers and bits,... along with set of Inverted Torx sockets,... in USA Harbor Freight has numerous sets available








