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I got to M2/5 and M2/7 pretty easily. Just removing 2 bolts and removing panel under glove box. They seemed to be working fine.
So defroster (M2/16) and footwell (M2/15) should be working fine too, because they seem to be working as intended.
The left ones are left blend (M2/6) and fresh air (M2/21). What does M2/21 do?
Next time I will check M2/6 that should be easy to access. If that is not the problem I will check M2/21.
I got to M2/5 and M2/7 pretty easily. Just removing 2 bolts and removing panel under glove box. They seemed to be working fine.
So defroster (M2/16) and footwell (M2/15) should be working fine too, because they seem to be working as intended.
The left ones are left blend (M2/6) and fresh air (M2/21). What does M2/21 do.
M2/21 controls the amount of air that blows onto your face (as opposed to the defroster or the footwell). The "fresh air" bit is a misnomer.
M2/21 controls the amount of air that blows onto your face (as opposed to the defroster or the footwell). The "fresh air" bit is a misnomer.
Hi, if I'm not getting heat or AC from the centre and side vents, would this be M21 or M6/M7? I'm a bit confused as to which one it would be. Both the sides/center vent failed at the same time so I'm inclined to think its M21?
The air direction to the footwell and defroster works fine.
M2/21 controls the amount of air directed towards your face. M2/6 and M2/7 control the temperature of the air to the L and R sides of the car respectively.
Just want to clarify that you are having a temperature problem and not an airflow problem. You are able to control how much air goes towards your face/feet/windshield by turning the direction dial?
M2/21 controls the amount of air directed towards your face. M2/6 and M2/7 control the temperature of the air to the L and R sides of the car respectively.
Just want to clarify that you are having a temperature problem and not an airflow problem. You are able to control how much air goes towards your face/feet/windshield by turning the direction dial?
Actually there's no problem with the temperature. I can get heat/ac if I direct through the foot well or windshield. I just don't get airflow in the centre or L/R vents that blow towards the face. Based on what you said above I should take a look at M21 then?
I pretty much had a burning smell come from the centre vent one day and now I don't get airflow blowing towards me when I set it there.
That is correct. I would start looking at M2/21. Guessing something cooked if you smelled some burning right before it stopped working.
While you have everything opened up, take a look at M2/15 (controls the footwell airflow) as well. That one has the highest failure rate of all of the motors for some reason. Also make sure you have the updated (beefier) footwell linkages installed. The old ones have basically a 100% failure rate. The dealer sells a kit with all of the required bits.
Last edited by slammer111; 07-07-2022 at 11:19 PM.
My center vents and passenger and driver side almost don't work.
Cold air is very low and I got no hot air.
No clicking noises, so maybe a stepper motor is dead?
Could someone guide me in the right direction? What is the one I have to check?
I fixed this problem. M2/21 motor was bad, so vents were stuck on closed position.
Time to do this entire exercise again for the 3rd time. Total repair time was 6.5h including cleanup. Getting faster each time.
This time it was the fresh air (the one that blows air towards one's face, M2/21 or M2/19) stepper. Started a few months ago with an occasional random click. Thought I could put up with it until next summer since I had already done several major maintenance jobs this calendar year and really didn't feel like doing yet another one. 1 click turned to 4-5 clicks after a few weeks. Another few weeks and it was now clicking continuously, for minutes at a time.
The MB PN is unchanged at A203-820-16-42. However, the internal Behr PN has changed from EAB501 to EAB502. No idea what they changed, but hopefully it has something to do with making the gears more robust. The 1st 2 failures were definitely the gears, This time though, I'm not too sure.
Also note that the OEM box has an expiry date for some reason, which isn't even tied to the date of manufacture. It's like the motor expires X years after some guy packs it inside the pretty overpriced box.
Stepper motor A203-820-16-42
The job is actually not terribly difficult, but the trick is to keep track of where each fastener group goes. My solution was to take a photo of the fasteners on the car, then stick them into each compartment sequentially. To get to the middle (2 or 4, depending on whether or not you have dual zone) motors, it only takes 11 or so groups of fasteners. Not too bad. These ones are the easiest ones to reach. The worst one for single zone cars is the windshield defrost, and for dual zone it would probably be the internal cabin filter one.
Fasteners
As mentioned before, I couldn't see any damage on the gear teeth. However, I could clearly tell that the clicking was coming from within this unit. Something inside was broken.
Stepper motor gearbox
The sound this time around was different from my first 2 failures, both of which were caused by broken gear teeth (dull thudding noise). This time it's a loud ticking (snapping?) sound - almost like that of an electric arc. Wonder if it's the actual stepper motor (electric drive) this time. I've attached a video of the noise. Hopefully someone can chime in.
Last edited by slammer111; 10-12-2023 at 03:14 AM.
02-01-2022, 10:31 AM
Total repair time was 6.5h including cleanup. Getting faster each time. 
