I have a 1999 Audi A6 Quattro; during this hot summer, anytime I drive slow like in traffic or when the car is idle, the water gage has been going up and anytime that happens, my A/C blows hot air. I replaced the coolant, but that did not fix the problem.
Could it be that I need to replace the thermostat? Or something else might be wrong with my car?
Thanks for any tip.

 

Have your fans checked.

 

Same thing happens to me n like bob Martin said I think it may b one of d fans not working, I was just checking mine right now n d little one on d passanger side between engine n radiator seen not t b working? I don't even know where to look? Lol I guess fuses or d wires on d fan!

 

I would truly appreciate if you can let me know what you are doing to fix this problem. I told the mechanic I need the thermostat replaced and he agreed to charge me $700, but I had a second thought to come on this portal to get some advices because it may be something that simple that I could do without the mechanic.

 

700$ to replace a thermostat????!??
That thing costs between $10 and $50 but does involve getting close to a timing belt change. I cannot believe paying that much for it at this time.
However it is more likely to be the cause then the temperature sensor since your car really seems to get hotter (while the sensor will just let the car think there is a problem, where there is not).

So yeah I like Bob's Idea right now much better:
Check your fans and if needed get them replaced.

If it turns out not to be the fans, you will have to get involved more. How far along are you for a timing belt job? If close, consider doing that and flushing out the radiator at the same time. A timing belt job will give you (or mechanic) easy access to the thermostat, water pump, tensioners and pulleys however this is a major job which will costs some serious bucks.

 

Thanks guys, I noticed after I turned on the A/C that only one fan was turning. The fan on the passenger side was not working. I will definitely visit a different mechanic in the morning to find out how much it could cost me to get it fixed.
Thanks guys! At least, I will be saving $700.

 

It could be fuses, relay/fan module, or the fan itself.
Check the easy one, fuses first. Check if the fan is dead.
https://www.audiforums.com/forum/aud...t-come-131980/
https://www.audiforums.com/forum/aud...ng-fan-102288/

 

Unfortunately $700 sounds about right. But make sure to replace the timing belt, water pump and the related stuff if you are heading this direction. It will run you more than a grand.

Like Bob said, check your fans first. That is the cheapest things to deal with at this point.

 

I checked the fan and realized that only one fan runs when the A/C is turned on. I checked the fuses located on the driver’s side and it is ok. Can anyone tell me where the fan relay is located on a 1999 Audi A6 Quattro Sedan?
By the way, I replaced timing belt + tensioner last December 2010 and so far, I drove only about 4,000 miles since replacing the timing belt.
Thank you for any tip.

 

Relays are located inside the driver side knee trim panel. Search for relay diagram and it will show you what they are.

Did you check the fan switch? Secondary fan switch is located in the lower coolant hose located at the passenger side of the car. It looks like the engine coolant temperature sensor. If you disconnect the lead going to the sensor, and jump 1 & 2 pins it should spin the fan at low speed. 3 & 4 are for high speed.