PaulW

This is the first really warm day in Chicago this year, my 07 S8 was parked outside for a few hours, it was very warm in the cabin. Turn the car on, drive away, no cold air coming out of the vents, but air is blowing normally, turn the temperature way down, the fan turns up to 12 speed. But it never gets cold.

So I was thinking it was a refrigerant leak, but after looking at it and cycling the AC unit to ECON mode and off, I could hear the compressor click on and the pipe in the picture below would get cold as soon as the compressor would kick on. It gets really cold.

So I'm guessing it's not the refrigerant charge. I think the orifice is between the two highlighted parts below, where one is hot and the other is cold.



Then I went to VAG-COM and there was no fault codes stored. I performed a component output test, and everything appeared to be working normal.

I figured it's something not allowing the air to go across the evaporator. I don't know how to do an adaptation of the components.....I don't know if that would help.

Any ideas on what I might look at next?

MP4.2+6.0

(Duplicate of my QW reply since others post here on AC too, especially with the heater valve DIY's soon waning as the temps go up...)

Late last summer I went through a bunch of guessing on why my AC didn't seem up to snuff lately. It would cool, but at first it was kind of musty and often was still blowing kind of warm for a couple of minutes--versus very reliable and blowing cool very quickly that was my prior D3 (and C5 4.2) norm. I tried things like your outside sensor change--as well as the inside dash one--helped some, but no cure. Also suspected the heater valve for a while. No codes and all the VAG COM diagnostics suggested things were fine. Compressor always worked, fan cut in when turning on A/C, etc.

Had the car in for TCU updating at the local dealer and had them take a look at it. With no known leak, they found it now had 300g of refrigerant by weight, vs. 620 at spec IIRC. They inspected it and filled it up to spec, and all better.

As I thought about it further, I remembered reading previously manufacturers have reduced system capacity in general with newer refrigerants, in part to combat climate issues even with the newer formulations. But that leaves less in the system over the extended years to keep going.

Net, springing for the refill seems to have done the trick for me.

TSHong

Paul, I would also check the amount of refrigerant. Our system holds roughly 1.5 lbs of R134A. I was a little low and had the ac stop working on a long trip. I think it froze the evap. Any way, I vacuum out the system and added the specified amount of refrigerant and it was much colder than before. It will quickly cool down on a hot ATL day.

Also hit me up the next time you come down. Yu have to see the W12.








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PaulW

Thanks! That was weird, none of the replies showed up until I refreshed the page a few times.

PaulW

It's fixed now.

You were right, had about 300 grams (system is 620 grams), it was evacuated, charged and works normally again.

$155. Brought it to an independent.

MP4.2+6.0

That is, feeling like 7 or 8 year old D3's may often need a recharge by about that timeframe/cycle. We both came up with almost the same depleted amount pre-recharge. Mine is a 2006 with a mid 2005 in service date and 100K miles when it was recharged.

ltooz_a6_a8_q7

I still have about 6-12oz cans - My D2 needs 1 can every summer (ice cold).

Cheers,

Louis

MP4.2+6.0

to 40+ g. per year of age since prior A/C service. Only two data points, but they were pretty similar and we both had the service professionally and w/ weight calcs. If I have car for more years, what I will probably do since I have my own car's data point.