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General E46 Forum
This is the place to get answers, opinions and everything you need related to your E46 (sedan, coupe, convertible and wagon) BMW!

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Old 07-20-2013, 11:08 PM   #1
sannouni
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Join Date: Oct 2010
Location: Montreal, Canada
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My Ride: 2005 330XI
AUC (Recirculation) Sensor Question

I got a code (AUC Heating) from PA Soft..... I tried cleaning the AUC sensor as per (http://forum.e46fanatics.com/showthr...ht=auc+heating), my sensor looks a little different than the one in the DIY (body looks the same, but the sensor itself is not pointing outwards, it's pointing to the side of the housing)

Welll..... i'm still getting the code

should i give it a shot with some MAF cleaner or Brake parts Cleaner , has anyone done this ?? (cleaning the sensor using a vaporizing liquid instead of compressed air)

the part is available here (http://www.ecstuning.com/Search/Site...7001/ES176686/) but i dont want to spend the money without making sure that the sensor is faulty beyond repair

Here is how the sensor works (http://www.figarosensor.com/products/822pdf.pdf) and here (https://www.appliedsensor.com/pdfs/A...VBeyondCO2.pdf)

again, i dont have much experience with Air Quality Sensors... any input would be appreciated...

Edit: the code is (AUC Heating)

Last edited by sannouni; 07-28-2013 at 12:32 AM. Reason: putting the exact code from PA Soft
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Old 07-21-2013, 12:53 AM   #2
scottjoh
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AUC (Recirculation) Sensor Question

The sensor has a finite life and needs to be replaced.


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Old 07-21-2013, 02:02 AM   #3
sannouni
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thanks for the response scottjoh, but really, everything i know of has a finite life...

I'm trying to conclude (and to be certain) that the sensor is faulty and in fact in need of replacement... one thing that could cause the the code, for example, could be that there is a conductive film that developed over the two terminals shorting the heating element, that is why i was asking if anyone has experience cleaning it using a more aggressive method (brake cleaner, electric contact cleaner, or i think more suitably, MAF cleaner)... one fact that is making me doubt that the sensor is faulty is that the production date is 03/09/2004 (printed on the sensor housing), which makes it one of the newer units in terms of age (there are ones from 1999 that are still functioning in E46s all over the world)

in any case, i have nothing to loose, ill try to clean it using a Mass Air Flow sensor cleaner, and plug it back, if it works, then i'll report back, if not, then i'll just order a new one...
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Old 07-24-2013, 09:48 PM   #4
sannouni
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just to follow up, tried cleaning it with MAF cleaner, nothing helped, code still shows up... ordered a new sensor from ECS (Part number: 64116917001)
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Old 07-24-2013, 10:36 PM   #5
scottjoh
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Quote:
Originally Posted by sannouni View Post
just to follow up, tried cleaning it with MAF cleaner, nothing helped, code still shows up
So let me get this straight. This delicate tin dioxide thin film detector which can detect extremely low concentration of VOCs, as low as 50 parts per Million, was just completely bathed in the very chemicals it is trying to detect. I would say that that isn't going to help it any.

Quote:
Originally Posted by sannouni View Post
I'm trying to conclude (and to be certain) that the sensor is faulty and in fact in need of replacement... one thing that could cause the the code, for example, could be that there is a conductive film that developed over the two terminals shorting the heating element, that is why i was asking if anyone has experience cleaning it using a more aggressive method (brake cleaner, electric contact cleaner, or i think more suitably, MAF cleaner)... one fact that is making me doubt that the sensor is faulty is that the production date is 03/09/2004 (printed on the sensor housing), which makes it one of the newer units in terms of age (there are ones from 1999 that are still functioning in E46s all over the world)
The sensor is very similar to that used in CO (carbon monoxide) detectors which Figaro also makes. These sensors wear out and must be changed periodically. The home CO detectors makers used to sell replacement sensors, but, now that many states require them they just suggest that they entire unit be replaced very so often. Recommended change interval is something like 3-5 years.

I have a 1999 E46 and will never complain that my AUC sensor isn't working. You know why, because my car doesn't have that sensor. The AUC sensor is only used on cars where the HVAC control unit has two circles with an "A" on the recirculate button. My car only has a since circle and no "A". I don't know when the Automatic Recirculated Air Control got phased in or if it was an option. I know that all US bound E46s got Automatic HVAC, but, that only regulates the temperature and varies the fan speed automatically. In other parts of the world Automatic HVAC was an option and the cars without it got a control unit with two big knobs. One for hot air/cold air mixture and one for fan speed. The good thing about that system is there is no final stage resistor to go bad.

Last edited by scottjoh; 07-24-2013 at 10:43 PM.
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Old 07-24-2013, 10:52 PM   #6
sannouni
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good points scottjoh... i was loosing the sensor anyway, so i tried with the most aggressive treatment i can give (without making things worse)

most of the E46s in Canada that i've seen had that sensor...

i dont want to jinx the FSR/FSU but it's working well so far...
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Old 07-28-2013, 12:34 AM   #7
sannouni
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again, just for the record, in case someone comes searching for this, the part costed less than a $50... after installation, and deleting the error... everything worked fine... error has not yet come back (it used to show up right after i delete the codes, or within one A/C control unit re-start)
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Old 07-28-2013, 12:55 AM   #8
Augster
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I noticed this error code in my system while checking it for another issue and wasn't sure what the error indicated or what component to examine. Glad this thread came up at the right moment!
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