I guess I acted too quickly and purchased the upgraded linkage arms that turns out were already on my car since it is an '05. Oh, well the clicking on mine turned out to be the footwell stepper motor. I removed it, took it apart, cleaned the internal gears which had gunk, and other small pieces of plastic that were "jamming" the gears as they turned, put it alll back together, closed the stepper motor, spun the output shaft 180 degrees so that the motor now can use the unused part of the gears when it moves. I then removed the next door neighbor motor(the stepper motor for the center vents on the dash) and swapped them. I did this because having to operate the long linkage arm requires more torque from the stepper motor so it should be easier for the "weak" motor to work the small gear for the center vents than that long arm. Anyways, I checked all plastics, mounted the motors in the new positions, synched them, No Clicking and full operation! So aside from the purchase of the two linkage arms that I ended up not needing, I was able to fix the problem for FREE... plus my time which was about 5 hours (mostly becausse the PDF's talk and illustrate everything BUT '05, that being said... they were still bery useful!). Now if I ever have to go back in there to replace that "weak" stepper motor because it does fail, it is already mounted in the center and not the harder to reach original footwell position. I'm so glad and happy that this is taken care of... my wife even noticed when she got in the car and started it and heard no clicking. Thanks guys for an awesome thread!!!

 

When I was younger I would have attempted replacement of the plastic arm on the stepper motor that caused the 5 or 6 clicking noises when starting my 2003 CLK320. I had it done for $516 at an independent garage.

 

I had this problem, it was the stepper motor inside the pollen cabin filter box, found the black 3-wire cable and then just cut it, 2 stepper motors disabled, 1 was for the pollen cabin filter box and the other was to recirculate the air so I've just positioned the flaps manually, does not throw up any errors on dash, problem is now gone, had to remove glove box to get access to cabling, could feel the clicking from the top of my dash.

Come at me Mercedes-Benz!

 

Not sure what you cut but all the stepper motors are powered and controlled from a single parallel 6 (?) wire ribbon cable that terminates at the HVAC control unit in the center dash.

 

Sorry yes you are correct, it was a parallel 6 wire ribbon cable, thats the one I cut. I'm not removing the entire dash just to replace a stepper motor that moves a flap.

 

Hi folks, car is all gutted and I've fixed one problem but as I feared didn't do anything to my reason for pulling it apart!
RHD 01 ex UK C240 wagon.
Driver's side does no hot air, only cold or fresh -ie set the drivers temp dial to max, things change and the air stops on that side, but no air warm or cold.

Before I replaced the broken linkage on M15, the sync did not stop, now it does (end on demist, I guess this is normal as when you first hit both buttons if fist sets demist then goes to alternate flash sync.) But no change to my main problem :{

I repaired the arm quite ok by 2 means - 1. found a switch nut in my junk box that I could screw onto the broken 2 bits creating a ring of support after superglueing, a bit like the washer idea someone else proposed, but this actuator has no problem with space constraints like the gear ones. 2. I looped some copper wire around the repaired item to add strength, and soldered it to hold in place. This actuator moves pretty easily it seems, so don't think it needs to be too strong.

SOO seems like the driver blend unit is likely the problem not giving hot air, but in a way that doesnt trouble the sync process?
All the diagrams are of LHD units so my problem is presumably M2/6 (why don't we use driver / passenger instead of left / right then all the mirrored names for us guys would be correct!?)

The diagram looks like M2/6 is floating in mid air, not very helpful to see just where it is. Anyone done the driver air blend unit and have any photos help on how to do? Do I need to take the top of the dash itself entirely off? Or can it be got by getting the steering wheel out of the way somehow? Took off the wipers and very disappointed to see this looks like no help at all!
Car is all in bits so would love a response soon so I can find the real problem and fix it. Hopefully someone has some clues to same me some hours and bloody knuckles!! Thanks

(PS also had grief getting the central cage out - when I did do I found the story online doesn't mention those 2 problematic tabs are made worse by an opposing one on the bottom of the same metal bar. I think it probably works a lot better if you remove by triggering the lower central one, not the upper 2. Will try put up some pics showing all 3 for others to know what is going on. In the end mine came mainly with BFI (brute force ingnorance)

Thx for all docs and pics that got me this far (but no cigar!)
Greg

 

[QUOTE=grege;5823477]Hi folks, car is all gutted and I've fixed one problem but as I feared didn't do anything to my reason for pulling it apart!..Before I replaced the broken linkage on M15, the sync did not stop, now it does ...But no change to my main problem :{

When the system goes through the sync process can you feel the air coming out of ALL the individual vents as it exercises the flaps? If so then maybe the temp sensor for left/right (?) side is faulty.

 

Interesting thought, sood to have some other ideas!

But when you take the driver control to cold it blows plenty of cold, to hot it stops blowing cold, but doesnt blow at all, sounds blocked.. Dont suppose there could be something else blocking the air - a bit of paper across a channel?

Greg

 

Once again.....does forced air come out of ALL the vents when doing sync?

 

Did your wagon come equipped with the charcoal activated filters located inside the vehicle? If it did then there may be four more flaps/stepper motors that have to be considered. I know this doesn't immediately help you but it could help us help you since we didn't get the Wagons here in the US.

 

Just tried some more tests and at one point of the sync the right amount of air comes out the driver's vent. But under manual normal control its very poor to zero. I thought before that I was getting useful cold flow, but not this time I tired. Sync doesnt test hot air anyway? Doesnt seem to cycle for long enough to effectively show temp control.

On defrost there is also way more coming out the passenger defrost vent than driver, so seems in at least a couple of modes the driver's side is weak. But again in sync a good amount comes out. Does seem like either a control program is screwed or a sensor is lying and falsely shutting down that flow.

Other question on charcoal filter etc - I can see this units stepper numbers do match a proper C240 layout.

Maybe I need to get the diag put on it. I have a cheap canbus reader, will see if I can get any sense from it... Any idea where any temp sensors are located to check them?
Greg

 

I believe your analysis is right on. All sync does is exercise the stepper motors to both extremes of the flaps and put them in a known state....either open or closed. If you have air being forced through the vents during sync and it completes the test sequence OK then I would say the mechanics of the system are OK. I don't know where the sensors are. I don't have my C class info any more but I seem to remember a built in diag program that checks all the sensors and the values they are returning.

 

This is such an interesting post, but I cannot seem to find an answer for the symptoms I am facing. I have a '03 RHD C32 and recently have experienced the ticking sound on startup. All blowers seem to be working fine but I have not checked if hot air is fine. The ticking stops if I leave the charcoal filter button enabled on my climatic unit. I have found a piece of broken white plastic which looks similar to the linkage arms shown in the PDFs, but am not sure which part I should look at fixing.

 

Further report folks on my air vent issue. I looked at the W203 tech training which is available as a download on startekinfo.com (great resource where it has your car!) and see the attached pdf of the air blend function.
This shows the hot air passes thru 2 louvres. If either of these fails to open, you will get no hot.
I strongly suspect I have a stepper motor that works, and possibly one vent is connected but the other has lost a joining rod.
My cold air path is fine, all actuators pass the test, but no airflow (hot or cold) when set to heat. The left side delivers air even when the engine has yet to warm and its set to heat, the right doesnt do this.
The previously proposed temp sensor problem could still cause this effect I guess, but seems more likely to be another broken bit of plastic. I'll try to get the dealer to run a diag on it and see if they can confirm the sensor is ok, or anything more about the blend motor operation.
Greg

PS - I have an ELM27 cheapie OBD2 device to connect via bluetooth to a computer - any way I can use this to read the error codes for the Aircon? I have demo software which reads engine revs, temp, fuel balance, and such but not error codes. Would be good to be able to buy some proper software that reads this stuff...

 

If air....hot or cold....ever passes through the vent then it's OK. The way the stepper motor diag works it tells you if a link is broken. When the stepper motor takes a flap to an extreme it gives increased current feedback and stops moving, stores that location then goes to the other extreme and stores that location. That way the flap can be set by the motor to any opening size and control the volume of hot/cold air when mixing for desired temp. If the link is broken it never completes the sequence and the diags fail. But your scenario does sound plausible. I know it's maddening. I had my w203 dash apart so many times chasing problems I could do it in my sleep. One thing I did that helped was to watch it with everything apart....just hook up the cables...and you can compare both sides for operation.

 

Thx Mleskovar, but follow me on this - if the one stepper has 2 separate vents it operates as per the diagram (did you read it - there is an even better set that show air flow for all heat / cool settings) - both inlet and outlet to the heater core - there must be a link between the 2 locations, and if just one of the louvre sets stops the motor at each end of travel, the other in parallel may be broken and there is no way of telling from the diag routine. In fact could even be the case with one louvre of a set of louvres - if just one provides the end stop, no way of telling the others are functional or not!
Greg

 

There are two blend air vent motors, one for each side.

 

Update folks..
Decided getting at the tricky actuators by removing the steering columns and brace etc was a bit more than I should do, so took it to the dealer. They spent quite a bit of time and not 100% sure of all the problems they found / fixed, but they did find a plastic end-stop for one of the motors had sheared off, and needed to be glued back in place. Hope this is going to last the distance! Also replaced one of the motors, dont know if they really 100% proved motor was the problem, may have just done it anyway.
But for future diagnosers, seems like the self-check could complete, but the unit also not work properly if an end stop was missing as in my case and the motor drives mechanism further than it should. I think the cogs eventually stopped it when the teeth part ended.
I think there was something fixed also in the heater core bit at the bottom, but cannot say if my idea above was right or not, until I get a chance to talk to the actual tech who did it.
From what I have seen, I think these motors are way too strong for the mechanisms, and should be less grunty in order not to break the flap links / stops etc. Probably the 2-button check process is seriously in danger of flexing the stops and links more than they like, and is to blame for various bits breaking.
Greg

 

First time I've heard that you can pass the sync and still have a motor problem. I bet that motor was bad as they have internal clutches that slip when driven too far or if something gets in the way. The actuator arms were redesigned/strengthened around 2003. Glad you got it sorted out....that must have been a big repair bill.

 

Well car has been in bits for some time now, as after one fix by the dealer got the top vent going, was looking pretty good, but I noticed on a cool day that the demist vent was blowing only cold!! They had to pull the WHOLE top dash off again, go right back in, found another set of link arms that looked ok, but were somehow not working fully and ordered the next kit to replace those, and it now works there as well. They thought they had checked everything, but that one slipped by.
(I took it in to the dealer with the centre console out, and its been that way while we get it sorted.
And its still in bits as they now have to replace the cruise lever that didnt survive the steering wheel being dropped :{
(I am driving each week a 4-5 hr journey down and then back again, with the ignition and light switches tied up by string, releasing the hand brake by pulling on the little ball on the end of the cable, bits of stereo all over the passenger footwell, and the car looking a wreck inside. And without cruise which is SOO annoying. But the end is nigh, I hope.

Randomly my drivers seat tilt / raise stopped working. Thought it was related but not - was the wire on the recline shorting plus to chassis, which some others have seen. May post some pics on this for others in a day or so.

And yes it has been a costly repair - even after I spent most of a weekend fixing one motor arm, and giving the dealer the car half gutted to start on the rest of the work. Would have been even more if the dealer didnt trim things a bit for being in the local MB club)

 

Just replaced the motor & linkage + broken flaps at an independent Mercedes repair centre (UK, E. Yorks). Total cost incl. labour, el. check & parts = £385. Next day done.
Works fine now, a/c heats, cools & air flow all OK. This info for reference only, in case you consider the same type of repair.

 

Pls man i have the same problem with the tiking noise. Is only when i start the car for 2 minutes top also i i dont have air flow on the main mid vents , only on the sides , the round ones next to mirrors they blow air what do you think many thanks daniel

 

Jakalino, there have been cases where what breaks are the mid vent gears. These are different than the long linkages but still weak by design. Judging by your avatar, you probably have the ones before the redesign in '03 where the tried to address the issue somewhat by beefing up the linkages and gears but left the stepper motors the same which have also been know to fail (or at least the clutches in them).

The ticking sound you hear is your climate control unit trying to line up the vents when you start your car. It does this every time you start you car regardless of whether your AC was already running right before you shut your car off. Anyways there is a PDF document on here that will help you do this fix step by step. Be ready to replace a stepper motor or two while you're at it but at the least, make sure you have the linkages and gears on hand when you start the job. Good luck!

 

One question about taking out the radio, I have a 2002 C230 coupe with alarm and the radio has a small red flashing light when the alarm is active ( car locked). How do i remove the radio safely? key in/ key out? , ignition in 0? position 1? or does it matter?
thanks guys for all the great posts.

 

I just visited my dealer and was told my radio's serial number is in the car's computer and as long as the radio is returned to the same car, all is good, change the radio for a different one and the car's computer must be programed with the new radio's serial number.

As for the repair, all went well (took two days, one to tear down and one to put back together) my problem was the stepper for the defrost flaps and required removing the dash to access.
I had to go to the dealer for a couple of cosmetic parts ( sunglass bin under the radio-plastic got old looking and the slider flap door over the cup holder broke from age) before putting it all back together, big mistake walking through the showroom to get to parts.
I would say that it was a inexpensive repair, but I am off in the morning to trade in my car for a new one, those showroom cars are hard to resist!