I bought and S4 Cab in July 2004.

For identification I will number the air vents from left to right:

1 - Left of steering Wheel
2 - Center Left
3 - Center Middle
4 - Center Right
5 - Passenger

I have bought 2 Robinair AC Instant read Digital Fahrenheit/Celsius stick thermometers for measurements. I insert the thermometer in to the vent about half way and set it for Celsius. All measurements are in Celsius.

The problem occurs when running the A/C. Since I live in Florida I have not tried this with the Heat yet.

Initially this was an intermittent problem but since, I can create it consistently.

Vent 4 info:
- always the warmest by anywhere from 2 - 6 degrees
- fluctuates within a range of degrees greater than other vents
- fluctuates more often than other vents

This problem is most when the fan is all the way on and the temp is LO. However lower fan speeds and other temperature settings have similar measurements.

Yesterday, Audi replaced the control unit on the dash for displaying and setting air system settings by the driver/passenger. They said the sensors were detecting a 3 degree difference between sensors. After replacing the unit, the difference went away. However, this had no effect on my stick thermometer measurements.

The real question is what happens between the sensor and where the air comes out the vent.

I have take measurements on 2 other like cars on the dealer’s lot and found vent 4 is not the warmest. In fact it is more in-line with temperatures from the other vents. Additionally, vent 4 temperatures go down to 5 degrees where as mine will not get below 9.5 degrees. But Audi says it doesn’t matter because every car is different. So far, 2 lot cars are the same and mine is different.

Audi is being too reliant on diagnostic tools. I have asked them, are you writing software for a A/C system or a Diagnostics system. Diagnostics do not catch everything. The have been reluctant to physically inspect what is under the dash.

Prior History:

Test Drive: A/C was blowing warm air out of all the vents and the salesman took it to the shop and said it was missing fuses.

Prior to taking Delivery: The refrigerant was replaced

2 days after Delivery: There was a 8 degree difference between vents 1 and 4 so Audi replaced the refrigerant again which at the time brought the difference down to 3 degrees.

Any thoughts,

Thanks,

Doug

 

Welcome to the forum DJBadin!

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It sounds to me that you have a heat source below vent 4 that may be the culprit. Have you checked to see whether there may be something of that sort that may be the problem? If I'm not mistaken, the center vents are fed by a single hose and then branch off to the vents. If my idea is correct, then the change in degrees must be coming from a source near the vent.

 

Thanks for the tip. I am having difficulties get them to look inside the dash. They don't think there is a problem with the car. I have taken 1 step back. I have asked them to show me other cars on the lot and in particular show me one with the same symptoms. That will probably take another couple weeks.

Thanks again,

Doug

 

Good luck with this and keep us posted so that it can be archived. Thanks.

 

The Audi Rep says if I think there is still a problem, to take it to the dealership. Champion Audi of Pompano Beach that looked at it last says they don't want to do anymore work on it. When I bought the care Audi of North America said I could take it any dealership for work. Now Audi of North America says generally speaking that is true, but that any Dealership can decide not to work on it.

 

Just use the AoA rep for any problems you have with them (dealers).

Just curious, but is the difference in temp really that noticeable? Is it noticeable only by a temp gauge or an you really feel the difference just sitting in the seat? Maybe the dealer thinks you're just being picky. No judgement here on my part - just wondering if it is falling under the "too trivial for my time" category.

 

Initially I did not have any thermometers. I could feel the difference with just my hand. Thats when I reported the problem to Audi. The Dealer was the one to first use them. Come to find out, it is not just a difference between my vents, but 2 other cars on the dealers lots blows about 5 degrees Centigrade colder than mine across all the vents.