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F30 / F31 / F32 / F33 / F34 / F36 (2012 - current)
The sixth generation BMW 3 Series Sedan F30/F31/F34 and the first first generation 4 Series Coupe F32/F33/F36. Get the latest 3 and 4 series pricing from our ordering and pricing guide sticky thread.

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  #51  
Old 06-29-2020, 09:39 AM
Doug Huffman's Avatar
Doug Huffman Doug Huffman is offline
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Quote:
Originally Posted by ybkbmw View Post
Could anyone here try to verify that fresh air / interior air control works properly with AC on and outside temperature above 80F?
Mine works properly independent of temperature. IIRC the AUC sensor runs much much hotter than ambient temperature, as much as 300C. It has been a while since I studied its function, and I would like a test gas source with which to verify its function and sensitivity.
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  #52  
Old 06-30-2020, 12:41 PM
ybkbmw ybkbmw is offline
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I recently looked at fresh air control button functionality on four cars on local repair facility lot. It was well above 80F. Two had no fresh air with AC on, regardless of control. One stayed in fresh air with AC on but got stuck on interior when control cycled to M and back. Only fourth one worked as expected. Without the AC on fresh air control works correctly.
Question: which sensor is responsible for this abnormal behaviour?
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  #53  
Old 06-30-2020, 12:57 PM
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Doug Huffman Doug Huffman is offline
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Location: Washington Island, Wisconsin, thru Death's Door
 
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Mein Auto: CPO2012 X5 35d M57(E70)
B414
https://www.newtis.info/tisv2/a/en/e...sensor/R8EZFJj


Sensor for automatic air recirculation control

> E8x, E9x only IHKA

> E7x (only integrated automatic heating and air-conditioning system in High version)

The AUC sensor is fitted on the microfilter compartment. The AUC sensor detects the following pollutant emissions from spark-ignition and diesel engines:

Hydrocarbons (CH )
carbon monoxide (CO)
Nitrogen oxides (nitrogen monoxide NO, nitrogen dioxide NO2)
The junction box supplies the AUC sensor with voltage. The junction box electronics evaluate the data of the AUC sensor. The junction box electronics unit transmits relevant data to the IHKA control panel (via the K***8208;CAN).

https://www.newtis.info/tisv2/a/en/e...ioning/25K67rA

AUC Sensor
The AUC sensor is an air quality sensor and is used to control the ventilation in the vehi-
cle interior (fresh air, recirculated air) in combination with the IHKA control unit, depending
on how much traffic-specific pollutant the fresh air contains. This increases the well-being
of the occupants and reduces the amount of pollutant to which the occupants are sub-
jected.

The AUC sensor is a fully integrated system consisting of the sensor element, the signal
processing system and a digital interface.

A metal oxide sensor is used, which is extremely sensitive to different odors and exhaust
emissions that typically occur in traffic.

The signal processing unit calculates the air quality level by continuously monitoring the
quality of the fresh air. The IHKA control unit is notified of this via the junction box inter-
face. Depending on other parameters (ambient temperature, humidity, road speed etc.),
the IHKA control unit decides whether to allow the recirculated air request from the AUC
sensor (including determination of the duration thereof) or suppress it.

The AUC sensor is installed at the air filter housing in the E70.

An important task that is performed by the electronics is accurate control of the sensor
operating temperature. The sensor element needs an operating temperature of approxi-
mately 300C. The sensor detects gases that can be reduced and oxidized. The main
ones are carbon monoxide CO (gasoline) and nitrous oxide NO as an indicator of soot
particles from diesel vehicles.
__________________
Scepticism and Animal Faith (1923)
Scepticism is the chastity of the intellect, and it is shameful to surrender it too soon or to the first comer: there is nobility in preserving it coolly and proudly through long youth, until at last, in the ripeness of instinct and discretion, it can be safely exchanged for fidelity and happiness.
(The Works of George Santayana p. 65)

Eschew eristical argumentation. I am responsible for what I write, not for your understanding of it.

Last edited by Doug Huffman; 06-30-2020 at 01:03 PM.
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  #54  
Old 06-30-2020, 01:02 PM
ybkbmw ybkbmw is offline
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The title "Automatic air recirculation control sensor" assumes that sensor is only active during Auto mode. What does it have to do with "fresh air always on" mode?
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  #55  
Old 06-30-2020, 01:19 PM
ybkbmw ybkbmw is offline
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The automatic air recirculation control sensor evaluates the concentration of carbon monoxide and nitrogen oxides in the intake fresh air. If the automatic air recirculation control sensor has an emission level that is too high, then the integrated automatic heating / air conditioning system control unit (IHKA control unit) in the air recirculation function is automatically switched to (prerequisite: IHKA in the automatic mode).
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  #56  
Old 07-08-2020, 05:30 PM
ybkbmw ybkbmw is offline
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Does anyone here who has a working AC can test fresh air control? As I mentioned above only one out of four 3-series tested worked properly.
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