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Air quality sensor not working


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Hi, does anyone have experience of dealing with issues regarding the air quality sensor? I must admit I didn't realise what it was, when I first had the car I was curious as to why the aircon system had two 'AUTO' buttons. But after a good read of the owner's manual I figured it out.

However, the sensor doesn't seem to want to play. It's always in the re-circulation mode, that includes heavy traffic conditions (lots of exhaust fumes) or up in the hills (clean air) regardless of the sensitivity setting - I've tried them all. I suspect there is some issue or other with it and I'm guessing that it sets itself in the re-circulation mode when it detects a fault. I've removed the sensor module and taken it apart, cleaned the little sponge filter (which tbh, wasn't all that dirty), put it all back and it's still the same.

It is possible to manually cycle between the 3 modes, so it's not too much of a big deal. Bearing in mind that when the folding roof is opened, it automatically switches the aircon system to recirculate, so maybe a faulty microswitch somwhere?

I just thought it's a rather cool feature to have when it's working properly!

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  • 3 weeks later...

Mine seems to be doing the same, thought it was a little strange how re-circulation mode is the default setting when I turn the car on and it stays there regardless of outside air quality.

I'll add that to the list of things that need looking at....

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I believe the auto air circulation mode takes two things into account.

1. The currently set AC temperature.

2. The air quality outside of the car.

When in recirculation mode, the AC can reach the desired temperature more quickly, since air from the outside needs to be processed, hence, the car will stay in recirculation node and then switch the mode to outside air. In heavy traffic conditions, the mode should be changed back to recirculation. At least this is how mine appears to behave. Mind you, the mode doesn't kick in instantly, rather, it may take a few seconds of driving through exhaust fumes before it does.

I also believe there is a smog sensor responsible for this, however, I am not aware of its location and potential replacement.

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I have taken the front bumper apart a couple of times, however, looking at the diagram, I'm not sure I understand where the sensor should be located. Couldn't find any videos on it either. If anyone has cleaned theirs any photos or info would be appreciated.

I also found an older thread somewhere on here that mention the sensor sensitivity adjustment menu.

To access it, set the air circulation mode to auto, then hold the circulation button until a menu appears on the nav console. There are 7 sensitivity levels in total, the default is medium. I've set it to slightly higher and will test to see if there's a difference. Not sure if this is available on models without the nav console.

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On 9/26/2021 at 12:15 PM, AntC said:

I have taken the front bumper apart a couple of times, however, looking at the diagram, I'm not sure I understand where the sensor should be located. Couldn't find any videos on it either. If anyone has cleaned theirs any photos or info would be appreciated. 

Hi Ant, 

The sensor in question is located in front of the radiator, fastened with a 10mm bolt. I'll post some pics and show the sensor location with a red circle. As I mentioned, I disassembled it and cleaned the filter but it wasn't that dirty tbh. I have no way of testing the sensor module, the connector appears to be OK after a visual inspection only, so I'm thinking the issue could be with the wiring or cpu. That's a tough one to fault-find without a schematic or wiring diagram. 

 

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Thanks for the photos Neil! 

Seems like its fairly easy to access. I'll make sure to clean it up when I get the chance even though mine appears to be working properly.

Cheers

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  • 3 months later...

Hey there, I took out the snog sensor today and most of its is clean except for the piece that's made out of some sort of fabric which is quite dirty. 

I did get any dust out of it but it's still quite discoloured. Anyone know if it's safe to simply wash it with water and soap? Also, would it be a good idea to clean the entire sensor with a MAF cleaner?

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Hi Ant, avoid getting any water/fluid or moisture in the sensor component. However, the spongey filter bit is easily cleaned with mild washing up liquid & warm water. Make sure that it is completely dry before refitting. HTH👍

Out of interest, I'd like to see the manufacturer's logic flowchart or operational truth table for this device. As I mentioned earlier in the thread it's a great idea for a gadget, but apparently in my case at least, somewhat questionably implemented. 

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Hey Neil, yes, its great in theory, however, I'm also questioning whether its working correctly or if its correctly implemented.

For example, I'll sometimes notice that the recirculation changes when I'm between multiple cars at a traffic light, other times, I'm seeing black smoke come out of a diesel in front of me and can even smell it, but the AC still draws air from the outside. Not sure if it's because the sponge thingy is dirty.

Will take up your advice on washing it with warm water and letting it dry when I get the chance and will update to tell if there's any difference in how the automatic recirculation works.

Cheers

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