Automatic recirculation HVAC fault - doesn't switch on poor air quality

Had my car checked, for the same issue and was told that the problem was that - "vehicle requires anti-bacterior treatment ($88 ) and a new pollen filter". the car is only 9mths old and has covered 15k kms. they suggested that is was because I used the auto - recirc setting as it traps foul air and causes the smell and I should just leave it on fresh air all the time.

I told them not to bother - isn't the point of the auto recirc. function that its only recirculates the inside air when it detects smells ? and the ac doesn't smell all the time, just occasionally when in heavy traffic.

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Originally Posted by mfl

they suggested that is was because I used the auto - recirc setting as it traps foul air and causes the smell and I should just leave it on fresh air all the time.

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That indicates that they don/t understand how the auto system is supposed to work. The auto setting leaves the flap in the fresh position for most of the time and only switches to recirculating under certain conditions such as reversing, bad air quality (alledgedly) and high outsie air temperatures.

The HVAC filters in the Golfs have an activated charcoal component that does remove odours, but has a limited life - mine is gone after only 10,000 km.

I'll be giving VWA feedback on this issue for sure - as a useful feature it still leaves a lot to be desired.

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Originally Posted by prise

That indicates that they don/t understand how the auto system is supposed to work. .

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Yes, I came to the same conclusion they didn't understand. I also had a another issue with them, the 'independent vw specialist' who serviced my car said that the turbo had a minor oil leak, the dealer said it was oil "sweat" and wasn't a problem. - at least they both agreed that the water pump was leaking.

- think I will just change the pollen filter myself.

Did they say how much the pollen filter was?

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Originally Posted by prise

Did they say how much the pollen filter was?

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no they just quoted $88 for the 'antibacterial treatment' but did not indicate if that included the filter or not.

A few months ago I posted on how slow the climatronic system in my Golf was to switch to recirculating air when driving through smokey exhausts, in tunnels, etc and how I was getting odours in the car. The dealer checked the system out and pronounced it working properly using LPG to trigger the air quality sensor. Since then I have tried a couple of fixes that had a positive effect.

1) I noticed that even with recirculating selected there was some odour coming into the car. Because I had doubts aboutwhether the recirc air flapwas closing off fully, I used VCDS to run the HVAC calibration output test that 'relearns' the open and closed position of the various air flap controls. After doing this I noticed that the closed position on the recirc flap motor had adapted to a slightly different value. Anyway that seemed to fix the problem of odours coming in after recirc was selected.

2) I had been using an ammonia based windscreen washer additive to help clean bugs (the standard alcohol stuff that came with the car wasn't that effective). I discovered that the ammonia was triggering the air quality sensor and with the run-off from the windscreen ending up in the same HVAC air intake area as the sensor, it had progressively desensitized the sensor. After I went back to an alcohol based additive, the sensitivity gradually improved and is now what I would expect.

wow had no idea that the car was that smart!

i'm suprised the dealer wasn't able to put settings back to default for you though

Driving yesterday I came to the conclusion that my air sensor seems to have gotten better with a few kms under its belt as it seems to be far better at keeping fumes out compared to when it was new. Later on I parked in a shopping carpark yesterday and upon opening the door was hit by a really strong smell of wood burning, obviously the sensor had stopped it from getting to the cabin.

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Originally Posted by prise

2) I had been using an ammonia based windscreen washer additive to help clean bugs (the standard alcohol stuff that came with the car wasn't that effective). I discovered that the ammonia was triggering the air quality sensor and with the run-off from the windscreen ending up in the same HVAC air intake area as the sensor, it had progressively desensitized the sensor. After I went back to an alcohol based additive, the sensitivity gradually improved and is now what I would expect.

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The 'fresh air' flap always closes when you use the car washers.

Stoney!

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Originally Posted by Stoney!

The 'fresh air' flap always closes when you use the car washers.

Stoney!

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I ran a test with the HVAC on and monitoring the air quality sensor output on VCDS. When I held a rag with the ammonia based additive on it near the HVAC inlet, the sensor output changed. The alcohol based additive doesn't seem to have the same effect.

The sensor is in the plenum chamber just in front of the base of the windscreen which is also where run-off from the RH side of the windscreen ends up before it drains out. Yes the fresh air flap does close when you use the washers, but that doesn't stop the sensor being exposed to the washer fluid.

Anyway, since I stopped using the ammonia based additive the sensitivity his improved noticeably.