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Discussion Starter · #1 · (Edited)
EDIT: I got a diagnostic tool and software and these errors stood out to me:

E70C2B: AC-LIN-1: Motor fresh air / dynamic pressure does not respond, bus error slave 15

E70C2C: AC-LIN-1: Motor circulating air does not respond, bus error slave 16

E70C2D: AC-LIN-1: Fan output stage does not answer, bus error fan output stage

E71429: Signal (Daten_Sensor_AUC in 0x2D0): received invalid

8011A9: Motor fresh air / dynamic pressure: blockage

8011AC: Motor circulating air: blocking

801207: Fan output stage: Interruption in the load circuit

Hi,

Noob here. I have a 2012 535i xDrive. And recently the cabin blower fan stopped working. Basically it will turn on for a few seconds, but then it slowly dies down and then turns off.

took it to a BMW dealership and they assessed that the issue was the speed controller (blower motor resistor?) which is located on the blower motor housing. They said they tested the blower motor itself and it seems to work fine (makes sense, as it will always turn on at full speed, but then turns off).

but they wanted $1200 to fix it. I said screw that, bought the part for $60 and replaced it myself.

After I replaced it, I turned on the car and got the exact same symptoms. Turns on at full speed (fan is set to max in the cabin), but then slowly dies down after a few seconds.

I’m at a complete loss now. I went so far as to completely remove the blower motor, hooked it up to a 12V power supply, and it does indeed work fine. And I highly doubt that the issue is with the speed controller, as I replaced that too with the same issues.

My buddy said the problem most likely lies with the “body control module” - I didn’t know what that was, but it does sound like a possible culprit.

Can anyone help me try to further isolate the issue?

Again this is my first post here so I apologize in advance if I posted this in the wrong section or something like that.
 

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02/2012 X5 35d M57Y CPO 121K miles NOKIAN WR G3 30K miles
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Hi,

Noob here. I have a 2012 535i xDrive. And recently the cabin blower fan stopped working. Basically it will turn on for a few seconds, but then it slowly dies down and then turns off.

took it to a BMW dealership and they assessed that the issue was the speed controller (blower motor resistor?) which is located on the blower motor housing. They said they tested the blower motor itself and it seems to work fine (makes sense, as it will always turn on at full speed, but then turns off).

but they wanted $1200 to fix it. I said screw that, bought the part for $60 and replaced it myself.

After I replaced it, I turned on the car and got the exact same symptoms. Turns on at full speed (fan is set to max in the cabin), but then slowly dies down after a few seconds.

I’m at a complete loss now. I went so far as to completely remove the blower motor, hooked it up to a 12V power supply, and it does indeed work fine. And I highly doubt that the issue is with the speed controller, as I replaced that too with the same issues.

My buddy said the problem most likely lies with the “body control module” - I didn’t know what that was, but it does sound like a possible culprit.

Can anyone help me try to further isolate the issue?

Again this is my first post here so I apologize in advance if I posted this in the wrong section or something like that.
Functional description
At the blower output stage, the control unit of the integrated automatic heating / air-conditioning system (IHKA control unit) specifies the nominal voltage for the blower motor. The nominal voltage is output by the IHKA control unit as a signal on the LIN bus. The activation of the blower motor via the blower output stage takes place depending on this control signal.

Blower speed is commanded by the IHKA control unit, a Pulse Width Modulated signal. Typically, the control module on start up commands a 100% speed and promptly 0% speed and listens to the motor spin down as verification of operability and condition.

How do you know that it “shuts / turns off”? One should not be able to hear the blower motor running. Air flow noises are a result of flapper motor settings.
 

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They diagnosed it wrong. Please order a blower motor and replace it.
I went through the same thing and had to go back and replace blower motor. I put in the old resister and it has been working well for past 5 months.
 

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Discussion Starter · #8 ·
Functional description
At the blower output stage, the control unit of the integrated automatic heating / air-conditioning system (IHKA control unit) specifies the nominal voltage for the blower motor. The nominal voltage is output by the IHKA control unit as a signal on the LIN bus. The activation of the blower motor via the blower output stage takes place depending on this control signal.

Blower speed is commanded by the IHKA control unit, a Pulse Width Modulated signal. Typically, the control module on start up commands a 100% speed and promptly 0% speed and listens to the motor spin down as verification of operability and condition.

How do you know that it “shuts / turns off”? One should not be able to hear the blower motor running. Air flow noises are a result of flapper motor settings.
You’re right, good point. I don’t know if it’s the flappers shutting or the actual spinning off the motor causing the noise to go away. I’ll further troubleshoot today.
Functional description
At the blower output stage, the control unit of the integrated automatic heating / air-conditioning system (IHKA control unit) specifies the nominal voltage for the blower motor. The nominal voltage is output by the IHKA control unit as a signal on the LIN bus. The activation of the blower motor via the blower output stage takes place depending on this control signal.

Blower speed is commanded by the IHKA control unit, a Pulse Width Modulated signal. Typically, the control module on start up commands a 100% speed and promptly 0% speed and listens to the motor spin down as verification of operability and condition.

How do you know that it “shuts / turns off”? One should not be able to hear the blower motor running. Air flow noises are a result of flapper motor settings.
okay interesting results. I confirmed that the blower IS still spinning, but with no air coming into the cabin. I was unable to determine the speed of the fan, but it is definitely still spinning.
 

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It is almost always the blower motor. Much more common than the blower output stage (resistor). If this is the original blower motor it has lasted longer than expected, at least in my experience.

It is a very easy DIY and you can get an OE blower fan for under $125.

My 2014 550i, 2007 335i and 2013 X5 all had the same symptoms at some point and the blower motor fixed it.
 

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Discussion Starter · #10 ·
It is almost always the blower motor. Much more common than the blower output stage (resistor). If this is the original blower motor it has lasted longer than expected, at least in my experience.

It is a very easy DIY and you can get an OE blower fan for under $125.

My 2014 550i, 2007 335i and 2013 X5 all had the same symptoms at some point and the blower motor fixed it.
Like I said in the post, I pulled out the blower motor fan and hooked it up to a 12v PSU. It works completely fine.
 

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EDIT: I got a diagnostic tool and software and these errors stood out to me:

E70C2B: AC-LIN-1: Motor fresh air / dynamic pressure does not respond, bus error slave 15

E70C2C: AC-LIN-1: Motor circulating air does not respond, bus error slave 16

E70C2D: AC-LIN-1: Fan output stage does not answer, bus error fan output stage

E71429: Signal (Daten_Sensor_AUC in 0x2D0): received invalid

8011A9: Motor fresh air / dynamic pressure: blockage

8011AC: Motor circulating air: blocking

801207: Fan output stage: Interruption in the load circuit

Hi,

Noob here. I have a 2012 535i xDrive. And recently the cabin blower fan stopped working. Basically it will turn on for a few seconds, but then it slowly dies down and then turns off.

took it to a BMW dealership and they assessed that the issue was the speed controller (blower motor resistor?) which is located on the blower motor housing. They said they tested the blower motor itself and it seems to work fine (makes sense, as it will always turn on at full speed, but then turns off).

but they wanted $1200 to fix it. I said screw that, bought the part for $60 and replaced it myself.

After I replaced it, I turned on the car and got the exact same symptoms. Turns on at full speed (fan is set to max in the cabin), but then slowly dies down after a few seconds.

I’m at a complete loss now. I went so far as to completely remove the blower motor, hooked it up to a 12V power supply, and it does indeed work fine. And I highly doubt that the issue is with the speed controller, as I replaced that too with the same issues.

My buddy said the problem most likely lies with the “body control module” - I didn’t know what that was, but it does sound like a possible culprit.

Can anyone help me try to further isolate the issue?

Again this is my first post here so I apologize in advance if I posted this in the wrong section or something like that.
Did you ever figure this out? I'm having the same issue.
 

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My only issue is that I've replaced the fan (it could be a defect, but it and the old fan both run with 12v applied direct from the battery). The old resistor was shot so I replaced it and now I'm getting the symptoms above, runs for 5-10 seconds, shuts off for a few mins, and so on. The new resistor is a cheapo one so maybe it's faulty?

Edit: I think it's a defective resistor. I spent an hour swapping between the two blowers and two resistors. The old one runs both fans at a very low speed and the new one runs both fans off and on but with full speed control while on.
 
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