HVAC and Stratification Flaps

[pjfox23]

AC is fully charged and starts blowing hot, on foot vents, when the engine goes above a certain temperature. Have a code for stratification flap.

I did some preliminary searching on this forum, and I didn't find much, just a bunch of complaining about the HVAC system overall

Does anyone have access to the schematics for the HVAC system in an F15? Specficially, the location of each flap?

[Qsilver7]

The HVAC stratification flaps are related to the stratified air dials on the center vent. They allow you to temper the air warmer/cooler:

The motor for each stratification flap (left/right) are M9/M69...the function of both are the same so I only posted the info for the left stratification motor. There are also other motor/flaps...like M21 is for the footwell & M20 is outside left motor flap...both of those can be seen in the illustration below...plus there are more flaps. Diagnostic equipment should be able to pull which flaps are having an issue:

[pjfox23]

Very helpful as always Q. Thanks.

Looks like the part number is : 64119321034

ISTA + error code is: E70C28 ; stratification flap motor, front right: does not respond.

After running the diagnosis further, it looks stuck (reports as 127% open).

Also, looks like there are 13 flaps total on F15...wow.

Give the photo you posted, I think I can get to M69 from passenger footwell and removal of lower navigation computer. Will report back...

[Qsilver7]

Good luck tracking down the culprit and getting it fixed.

[pjfox23]

Okay, so I dug in and found two relatively easy to access stratification flaps on the passenger's side.

One is where the diagram said, in the center dash. I think it is the M69 one in the diagram above - but can't really tell. You can access it by removing the glove box.

The other is in the footwell. You can access it by removing passenger trim under the glove box. I put a piece of blue tape on this one to differentiate the pictures.

I couldn't find the third one from the diagram (labelled X0011 above) - I suspect it is in the dash somewhere.

Anyway, I think it's the one with the blue tape that is throwing the code. I took both flaps out, and when I shake the footwell one, I can hear a rattle (the other one does not rattle). So, I switched both of them, and reinstalled. The issue is now magnified - way more error codes and no cold AC. I suspect the ones in center have more control associated with them.

Anyone know the pin layout for these flaps? I'd like to try to power what I think is the broken flap in order to see if it will spin (I suspect it will not).

Also, I did order a new flap, so when I get that in and install it, I will report back.

--

[Qsilver7]

...So, I switched both of them, and reinstalled. The issue is now magnified - way more error codes and no cold AC. I suspect the ones in center have more control associated with them. ...

When you say "switched"...do you mean you swapped the actuators to see if they would work in a different location?

If these actuators are like the ones in previous generations...you couldn't switch them around. In the past each actuator was designed to perform a specific operation...so if you put them in the wrong location, the system wouldn't operate correctly because the actuators were designed to operate when a specific signal is sent from the IHKA control module.

The scenario you describe...sounds like BMW has retained this old design element (in regard to the operation of the HVAC's actuators).

Make sure any actuator that is replaced...is done so with another actuator that has the same BMW part nbr...or one that was specifically designed to succeed the old part nbr.

[pjfox23]

Well, it turns out I didn't plug the HVAC control unit in all the way. Sigh. That is why I had a magnified issue. Always check connections.

Back to the original problem:

I got the new part in (attached). I swap it, and now everything is working fine.

So, two takeaways:

One, the stratification flaps look to be interchangeable. I did swap a working one to various locations, and it continued to work as long as I ran "calibrate flaps" in ISTA.

Two, anyone experiencing the original code above should consider changing the passenger footwell flap.

Thanks again.

[Qsilver7]

Great…glad you got it working…and thanks for the update.