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

[mr gee]

Here I'll give you some hooba


I find the auto recirc system to be gimmick and do not use it much. It is too slow to react and by the time it has switched I have copped a lungful. So I tend to select the manual recirc in the same maner as I would wind a window up before entering a tunnel or pulling in behind a dirty truck.

Prise, Bummer they cannot fix your system to your satisfaction. What makes you say the Auto recirc is not working? Mine just shows a Car Icon with the recirc arrow in it with "A" beside it. But there is no way to tell if the system has set itself to fresh or recirc onced in this setting. So could it just be that, because it is reactive and not predictive, you are also copping a lungful before it switches, leading you to believe it is malfunctioning.

I just hooked mine up to VCDS, looked at the recirc and air quality status. Started the car with AC in Recirc Auto and it indicated "recirc mode due to air quality" almost instantly and I could see the recirc valve close in VCDS. But then I turned the car off and did the same thing a couple of minutes later. Again in Recirc Auto. This time it did not sense bad air and indicated fresh. After two or three minutes with the engine running in the garage and well on the way to gassing myself it still had not switched. So I gave it away as it was getting way unsafe. Dunno if this was effected by logic related to start cycle and temp. Who knows but it would have readily let me gas myself before going to recirc. Gimmick I reckon.

Interesting that you tried a quantitative way to assess the sensor. I had my car serviced in June and the cabin air filter was changed. I thought I smelt more outside pollutants with the new filter and thought perhaps VW had replaced them with a plain filter. But I was wrong, the new filter is carbon impregnated. Looks like I need to look at my VCDS as well.

Did you notice if the sensor can be coded for more sensitivity?

[logger]

Did you notice if the sensor can be coded for more sensitivity?

I do not think so. However I did notice that the default coding of these units is set to indicate the sensor is not installed, when it is. Checked someone elses coding as well.

Would have expected bit 0 to be checked, however as you can see it is not. The coding would then be 0100000000 instead of 0000000000. However I am not familiar with the system. There could be a reason for it being set this way. ie inbuilt sensor versus remote sensor. One requiring coding the other not, or Ross-Tech could have their decode rrrs about.

[prise]

You can conclude whatever you want [/URL]

First visit - I'm told it is faulty and they have some indeterminate connectivity fault and will require the car for 3 days
Second visit - phoned 3 hours after dropping it off and told everything is working properly and the tech had talked to head office about it.

Reasonable conclusion - they didn't know how to test it the first time.

Look, I'm not having a go at the dealer (I am happy to keep using them). They appeared to be up front about it, had a loan car on offer and answered my questions to the best of their ability. Cars are becoming increasingly complex with all the features that get added each year so I accept they will sometimes take more than one go to work things out.

[prise]

What makes you say the Auto recirc is not working?

I drove behind an absolutely foul exhaust for over a minute (not diesel smoke) and the system did not switch to reirculating. I am familiar with the change in fan noise that occurs when recirculation is selected manually and I definitely didn't get the change until I gave up waiting for it and selected recirc myself.

Now the foul exhaust may have been predominantly burning oil but it was also running very rich so no shortage of HC's

Going through the Burnley tunnel yesterday I detected it switching just before I exited the tunnel so I agree with it being a gimmick. From what I've read car manufacturers are using a cheap (to them, not to us if Maverick is right about the $150 price) MOS sensor.

[logger]

Fair enough. Not working well at all. BTW, I was not for minute doubting you when I asked. Was just wondering if it was your nose or some indication on HVAC that was telling you was not working as it should.

[mfl]

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.

[prise]

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.

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.

[mfl]

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

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.

[prise]

Did they say how much the pollen filter was?

[mfl]

Did they say how much the pollen filter was?

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

[prise]

Lessons learned with Climatronic HVAC

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.

[SuperHans]

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

[hooba]

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.

[Stoney!]

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.

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

Stoney!

[prise]

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

Stoney!

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.