snagitseven

I can't remember what he said - it was six years ago. It only happened once at a year old when we owned the A4 and never repeated for another 40K miles. Maybe it was just an anomaly, who knows.

Scott Evil

I just read this thread https://www.audiworld.com/forums/q5-sq5-discussion-129/known-issue-c-wimps-out-long-runs-2887937/ it has some good information as well and seems to reflect our experience last weekend.

Also, i was sitting I the back seat with our sons, while my wife was driving and our au pair was riding shotgun. As my wife tells the story, they were both pretty cold and had increased the temp to 78+ degrees. Not long after that is when things got pretty warm in the car. The system was not set to recirc.

As I mentioned above, when we got home there was a telltale puddle on the garage floor showing the system was draining per normal. What was not normal is the amount of water--it was huge.

Therefore, I am going to assume the system did experience freeze-up due to the higher temp and higher humidity. We will use recirc on long trips going forward and I will have the system checked over at the next service.

My question to Audi, why not cycle the system into recirc occasionally to prevent this? Auto mode should be fully automatic.

Thanks for the conversation everyone. After being on AW for 15 years, it is cool still learn about these cars.

Redd

I would suspect the system was originally engineered properly, in terms of matching up the airflow, temperatures, ambient moisture, fin spacing, all so that it would not ice up. And then what is called a "forensic engineer" was called in and told "Can you find a way to make this cheaper?" and he said something like "Oh yeah, you don't need that custom fin spacing, the part from the model xyz is almost identical, maybe even has 5% more capacity, just use that one."
At which point the entire system design is destroyed.

Could just as well tell people to turn on the front heater/defroster on max. Or, install an auxiliary evaporator deicing coil in it. (Kinda like de-icing the carbureutors on airplane engines.(G)

Knowing Audi...I suspect that IF they can make the existing computers change AC modes, their fix will be to have the AC system go into a "defrost" mode from time to time to ensure this cannot happen. How to do that unobtrusively is of course a whole other ball of wax.

MartinQ5

Last week I had the same issue on my Q5. Fan was running but almost no air was coming out of the vents.

I turned off the AC button for a few minutes. During that time the air was still coming out cold. As it was over 30 degrees outside (over 86F) it should have get warm pretty quickly.

After 6-7 min, the air started to get warm, I turned on the AC again and the air cooled down and the air flow was normal again.

During winter I got a low AC pressure error. My dealer refilled my AC but could not find a leak. I suspect that there is a leak somewhere and my AC is again running low on gas making my cooler freeze...

When they filled my AC, the dealer added some "coloring agent" into the system to find a leak. I hope they will be able to find it this time.

Redd

Wow 30 degrees...here in the States we only need heat when it is that cold out.(G)

If there is a low pressure error, it almost always IS a leak, not just a bad pressure sensor. Presumably your dealer testing the amount of gas in the system (a pressure-vs-temperature test) and confirmed that. They are NOT supposed to refill leaky systems without fixing the leak, that only contributes to more "Freon" in the atmosphere, and in some cases, refrigerant techs can loose their licenses when they do that.

A system can be leak checked by putting soapy water on all connections (and the condensor and evaporator tubing for pinholes) but that takes time, and doesn't always show them. And requires tearing out enough interior to SEE the evaporator.

A dye test is somewhat better, if you start with a clean engine bay, but of course you still can't SEE the evaporator and you need lots of leak to get dye coming out the drain tube.

Then there is also an ultrasonic tester, specially pitched "stethoscope" with electronics that can literally HEAR the whine of escaping high pressure gas. Useless in a noisy environment.

And the heated-diode "sniffer" which can actually detect a leak as small as 1/4 ounce per year, as you run it past all the pipes and joints, and that pesky evaporator again. Two three hours labor no matter how they slice it, to access an evaporator properly. But the sniffer is often a cruel joke, because the techs are supposed to use it after the system has been pressurized (run) BUT WITH THE ENGINE OFF ANY NO BREEZE OR AIRFLOW, meaning the car should be in a closed off "box".

There are just so many good ways to find AC leaks, and so few shops that understand or are willing to do it properly. IF you've got a gross leak, they'll find dye dribbling out of it next week. If they can't find it, tell 'em to stop screwing around and get a pro to work on it.

A pro does his leak testing using dry nitrogen in the system, so there's NO refrigerant gas lost to the atmosphere. Since a leaking system has to be vacuum-purged and refilled anyway (to get out the moisture that is absorbed every time the system was shut down and sucked in outside air) and the receiver/drier has to be replaced at the same time anyway....doing it right doesn't cost any more, IF they are paying attention to the much more important things that just "topping it up".

MartinQ5

I am considering to bring my car to an AC expert instead of my dealer...

As for the 30 degrees, it was in Celcius. This is why I added a reference in Fahrenheit... Yes it can be cold in Canada... But not that cold in summer!

Redd

Yes, cold can be funny. We all seem to call "below zero" cold weather.

But here in the States, that's zero Fahrenheit.
Zero Celsius we just call a brisk winter day.(G)

MartinQ5

Today I checked my A/C radiator. On the bottom of it I noticed some green oily liquid. Could this be the coloring agent my dealer added when he refilled my system?

Could this explain my problem? Is it my exterior radiator that is punctured?

Redd

The exterior AC "radiator" would be the condenser.
Yes, the trace dye that they normally use is a greenish-yellow color, which glows brightly under black light. To confirm that is what it is, get a black light, put the car in the dark (or drape a blanket over the front end) and see if it glows. There should also be some traces left running down from the actual leaking spot to the puddle.

Normally those holes are not repaired, the whole condenser is replaced. The system must be emptied (by vacuum) then opened up. The condenser and receiver/drier are replaced (that has to be replaced every time the system is opened, it absorbs moisture from the system but has a finite capacity), the system is placed under hard vacuum to confirm no leaks, and then sometimes pressurized with dry nitrogen to doubly confirm that. Then vacuumed again (if it was nitrogen filled) and finally refilled with new gas.

Not a simple process, but there's no shortcut if you want it done right.

tomaszp72

Redd, you just described a sw issue. Why would it require a hw update? Just load a new sw into the memory and call it good. Just asking......