ND2020

So on rmeuropean with the part number listed, there's an OEM kit and and "EZ" kit. Which are you guys using? One better than the other?

jroach

Great thread. Used the directions to replace, in my case, a broken stepper motor.

Everything went great but somewhere along the testing or assembly process I tripped the SRS light. It might be related to having everything unplugged (radio, fibre, all the wires to the center console) when I started the car to test the valve flap motor (it worked BTW).

I have ordered a Carsoft scanner and will look at the code in a few days but when I was putting the center console back together there was a wire loom (I think it was three wires on a brown mimi plug) that was around the ashtray. I figured it was related to a feature I don't have on my car but ....maybe it was the seat sensor or ???. It wasn't the plug that connects to the "Airbag Off" light. I didn't have any more open palces to put a plug on the back of the console.

I'm wondering if anybody else knows what that plug might go to? I suspect this is just a matter of tripping the SRS light because I had the fibre disconnected when testing but thought I would ask.

jroach

I tested my new scanner, found three errors when running the airbag test. Cleared the three errors, turned off the car, restarted and all was clear.

Thanks again for a great thread! While this cost me a few bucks for the scanner I still saved hundreds.

If anybody needs to borrow a scanner in the Los Angeles area, let me know.

Darkman

I tripped the SRS light too. I had removed the instrument cluster and disconnected it. Then when I was putting everything back together, I didn't plug the instrument cluster connector all the way in by accident, turned on the ignition, the instrument cluster was dark, and the SRS light lit up. I reseated the connector, turned on the ignition, the instrument cluster lit up, but the SRS light stayed on. The only way to get rid of the SRS light is to reset it with an OBD scanner as you found out.

mleskovar

I had the same error with the instrument cluster but nothing removed during the stepper motor/links R&R should trip the SRS light. I also tested the motors with everything apart (several times ) and didn't trip the light.

jroach

One of the errors was something like...CAN Bus disturbed. While I had the dash apart I updated the Aux jack that I had previously modified on the radio. Radio was removed when I tested the stepper motor so I'm thinking that testing with the fibre temporarily broken might have been the cause but hard to tell. I thought I had tested once with everything removed and did not get the error but the next time I tested I did get the error.

Onericali

Can a faulty stepper motor or linkage eventualy cause AC probems? I use to have the loud clicks, and now nothing, but the fan works in all vents.

If the AC is off, but the fan is on, would there still be clicks?

mleskovar

Yes.

Yes.


The AC compressor shaft is always turning. Vanes inside the compressor are varied to increase/decrease pressure.


Right here. Search and you'll find what you need to know.

Onericali

Hahaha thanks a bunch, that helps a bit.

I used to have a lot of clicking on startup, and Im pretty sure it did it no matter if I had the air turned on or not.

Later, no cold air, and no clicking, however, my fan changes through any of my vents without any problem now.

What does the stepper motor do exactly? If it controls what comes out of the vents, then might my AC actually be working, and just, filtering out somewhere in the engine and not out of my vents? Lol. I'm probably way off on what the stepper motor does though. And its definitely worth opening my dash up and giving it a look.

I have heat and just room temp AC. If its not something like I stated above, its got to be a slow leak after the compressor or a weak compressor, because the low will stat at 55 and go to 95 in 70 degrees, but the high only moves from 65 down to 60.

Hard to trust anyone at a dealership, unless I know exacty what to tell them to check, etc... *Shrugs

OMG I actualy just hit the AC rest button and it gave me the clicks. No cold air though. Hmmm. Prob a slow leak, k thanks, lol.

mleskovar

Clicking at startup is usually the footwell vents. If the clicking stopped it's probably because the linkage fell off.

Are you sure you checked the footwell vents?

You're correct, they change the position of the flaps that mix air and direct air flow through the vents into the cab. Your AC may be OK.

Onericali

I feel it blowing hard on my shins, but that is all the check I have done.

As far as your news about the stepper motor perhaps being the culprit.

Boy is that exciting. Will tackle this ASAP.

Wait, why would my high side pressure be 65 with AC off then go down to 60 when on in 70 F weather? Low side went up from 55-95. Isnt that high side pressure low? Even still, it might be the stepper motor mixing along with a slow leak or something.

Thanks

15 bucks (if allowed) for whoever guesses the right problem of mine first.

NYFlapjack2

2002 C230K coupe, basic HVAC controller (not digital).

Thanks for so much good info here! Yes I believe I have footwell stepper motor and or flap arm issues.

I apologize if I missed this answer as I did reviewed this entire thread. Printed out the full MB HVAC PDF tutorial and studied this before asking.

My car clicks, goes through usual entire "battery disconnect" routine and does not end or find home. Also when then the 1st car starts up it does the clickty clack, and I estimate an ODD amount of times moving checking,? but it does stop searching for limits.

My footwell openings dispensing air are 50/50. My work around for now is, with manual flap selector pointing full to floors, I start my car and immediately put HVAC in manual, inside to recirculate and full blower speed...and the clicking starts and ends per normal in a few minutes. Then half the time it has full foot heat, half the time you can hear it is fully closed and air pressure deadheaded going no where. So half the time I leave it in manual and reduce blower speed and I have floor heat. Other times when deadheaded I move selector up and depend on upper vents. No biggie for now as defrost on demand is fine.

It goes through the entire battery re-orientation and start up with full blower - all openings rotating the air flow to all ports on & off fine. It appears all flappers move fully open and close, as they all shut off or supply. So it acts like the footwell stepper arm is hooked up it just doesn't find the limits to its stroke ends (internal in the motor or the gear?).

So I don't think I see pictures of a stepper in those details and or describing that failure - is it a stripped stepper? or does it have limit switches at each end of its range?

Again apologies if I missed it.... but what is the gear in the expensive kit look like? Are there any detailed pictures and how the 3 look like, how do they work together (on the bench even)?. Blower motor on high helps an ailing stepper motor move flappers?

Do I understand the kit comes with extras you may have? Anyone got a broken one? As a employed rapid prototyper and reverse engineering fella maybe perhaps a tray of the package of these growing in a SLA or FDM machine would be a nice pay day and desirable?

I already have 2 new style arms and I will buy a motor if the consensus is just do it too (frankly I am leaning that way while I am in there). But do steppers come with and or think I need the gear(s) too?

mleskovar

I'm not an expert but I've had my dash apart 4 times to repair HVAC failures so let me try to answer your questions.

What do you mean by "battery disconnect" routine? And by "click" do you mean the key handshake? And by "find home" are you referring to the clicking after start up?


There's no physical limit switches for any of the motors/actuators. It's electrically controlled with resistance feedback and electronics within the motors. If the 'clicking ' is at start up and cycles about once every 2 seconds then stops after about eight tries then that usually points to the actuator arm that's attached to the motor. If it's a louder "snapping" noise that can start or stop randomly or never stop it's usually the stepper motor.


The "gear" is just a sector gear attached to the actuator arm. I've seen pictures of the 'kit' and don't recognize some of the parts.

Which arms do you have? Steppers come without gears, same motor for all locations. Arms fail more than motors but both fail.

NYFlapjack2

Ahhh resistance at limit ends...I get it!

Then like others I sense my failure mode (as pictures I've seen here of some arms) is the Hex socket / shaft area cracked and I bet the shaft never stops as it is acting rather like stripped out?

To answer you ...well I know I am confusing - both the HVAC battery full disconnect like replacement, where you press & hole 2 buttons to start the re-synch limits. As well the start up it cycles... both all air vents produce & shut just never set to final limits I guess... It is not random, just at initial start up, once on the road I either have foot well opening or not until next time I leave the car and return to my routine start up.

From what I read in others descriptions here I believe my noise is flappers slamming with attached arm (or stripped on the shaft?) but not the click of a stepper motor and its internals.

Regardless to avoid going in there twice : ) .. I plan to buy a motor and replace it anyhow The 2 new arms I have the beefed up style with added mass around the hex socket MB # A 202 830 00 33.

Still don't know what or how the gear is in there that folks mention.....

Thanks for the reply!

mleskovar

Bingo!

Resynch diagnostics, that's what I thought you meant.


All of the actuators aren't identical. Some have a sector gear attached. You'll see once you get it apart.

d4jmo

great photos great help thanks

Silver C

There is a very slight and soft hissing sound when my AC is on..

And also when I turn my knob for hotter air (25c), there's a low humming noise..

What could it be? Thanks..

Onericali

I just did this DIY and the stepper motor linkage looked fine and intact.

Is there anything else I can do productive for AC diagnosis while I've got it apart?

mleskovar

I assume that you ran the diagnostic program and it failed, and that's why you took it apart. Run the program while you have the dash off and listen/observe the various flap actuators to see which one fails.

Onericali

When I ran the program as you say, it just kept going, it never stopped.

That being said, I just opened it up to make sure, because I'm having trouble diagnosing whether its my compressor or a slow leak.

The reason for the trouble is that I have normal low pressure, but I'm showing low high pressure, so, I've been worrying about bypassing the sensor somehow to get the uv leak fluid running through the system and having the compressor run, which might hurt it.

Thank you for the response, and ironically, I only checked one of the arms. I'll pull the foam out and check the others.

Thanks :=)

mleskovar

That means it detected a failure. You need to find which motor/flap combination failed. Sometimes the actuator arms break to the point that the motors just spin in them and don't make any noise (clicking).

Onericali

Ah I see. Ty.

So.... I did what you said, and this is the result!:

For the two stepper motors to the left behind the radio:

The far left one, where the linkage goes upward behind something so I can't see, well it keeps slipping and falling back down. That is the M2/15, the left and right footwell flap positioning motor. However, both my foot vents work fine. It makes a small click, but seems to work.

The one inner the far left one (there are only 2 there for the C230, and 240 and G500 I think. Well, I believe that is the M2/21 fresh air flap positioning motor. It has a horizontal linkage connecting two sets of plastic gears. They seem to be rotating smoothly.

That is all I saw for the test.

Now let me tell you how I ran the test:

1) I Held the Defrost button and the Recirculation button in until they started flashing alternatingly.

2) This keeps running infinitely, going through the test, until I hit one of those two buttons again.

-At this point, the system stayed quiet for a bit, then seemed to run through the test again.

3) I took the key out to stop the test.

I don't believe this DIY covers how to see the other motors.

What I'm hoping for is that the M2/6 blending motor was broken, and the bad blend of air and temperature caused some sensor to trip and stop the compressor from coming on.

(Could I test this sensor seperately?)

If so, I will need to get up higher behind my dash to see the M2/6, which should be right above the far left motor behind the radio.

PS: Can I drive with all this stuff out?

mleskovar

The linkage is broken, if you remove it you'll see. Cracked around the hole that the motor shaft inserts in. I bet if you replace it, then run the test, you'll get an all clear on the test sequence.......which is, it sequences all the motors/flaps then stops.


That would be great but first try what I suggested to see if they pass diagnostics. There's been a few bad compressors.


QUOTE=Onericali;4595185]...(Could I test this sensor seperately?) ...[/QUOTE]

I'm sure you can but I don't know where it is or how to test. Check out some of the AC threads.

QUOTE=Onericali;4595185]...PS: Can I drive with all this stuff out?[/QUOTE]

I don't see why not. Just be careful.

Onericali

Oh okay I see now thank you so much.

Now I just need to figure out how to get to those two motor screws that are exactly behind the left brace where the radio was.

The only thing I can think of is using a T20 bit without a socket and using pliers to turn it.

What a major pain. My T20 screwdriver or 1/4 T20 socket can't reach it.

mleskovar

If it's mounted like the C320, and I think it is, grab the whole assemble and twist it until the T20 screwdriver can access it straight on. That whole assembly is plastic and flexible (if I'm thinking correctly)....