Starting earlier in the summer when I was sitting at the bank drivethru one day I had my AC on. I noticed it started get warmer and warmer and then noticed that the car itself started to overheat. I have a 2001 A6 2.7T and noticed also that the temp gauge that reads the outside temp. was showing 110 Degrees. I left the bank after letting the car sit for a bit and once I started driving it the "outside temperature" reading slowly went down. When I got home and shut off the car the fan continued to run even though the car was off as if it needed to cool of the engine more.

I ended up leaving that same day to study abroad in Korea for 7 weeks so figured I would fix it when I came back. I noticed that the outside temperature reading still reads high if I am sitting in one spot and not actually driving. Also the car shows occasionally that it is over the halfway line as far as temp. of the engine but again this tends to lower once I am driving. Finally this only occurs when I use the AC.

Can anyone diagnose the problem for me? I am thinking that it must be something to do with the fan that cools the engine or something of that nature but still think it is odd that the "Outside temperature gauge" always reads much higher when I am sitting in one place. Again I am new here, thanks for any help!

 

Water pump is bad, change the thermostat while your in the timing belt area too. When the engine reaches a certain temp the engine management will shut off the a/c compressor to prevent major damage.
The cars are smarter than we are.

 

I am in NO way doubting that it is the water pump but why wouldn't I get a check engine light if it was the water pump? Also why would the problem be fixed while driving more than, say 35 mph, at this speed the air conditioner works great and there is no sign of a problem. Again just trying to understand it myself as this is only my 2nd car, I am young and kinda wanna know why this would happen in this way. Again thanks a great deal for your help.

Also how easy is it to change the water pump yourself? Do you need to drain the cooling system first in order to switch it out?

 

I wouldn't expect an inefficient cooling system to throw a CEL.
In addition to water pump and thermostat, the issue may lay with the radiator, fan, fan clutch, or coolant level.

 

Coolant level is fine, however I was worried the fan might be an issue since it continued to run the first day there was an issue....even with the key out of the car and the alarm set it continued to run. How would I go about diagnosing the problem without having to take it in?