Ive been having a cooling problem and I assumed it was the fan(it was)switch so I replaced it and car began running at proper temp once driven for a few miles. However it has gotten very cold here in Chicago -27 last night , and the car is no longer getting to temp,especially on the highway or just sitting idling. Who makes the best tstat. Ive read that wahler makes the oe but also that stant is just as good, any opinoins

You probably did have a failed fan switch and it's good you're taking it one step at a time. But yeah, it should be coming up to temp and you should be getting good hot air out of the heater vents.

and I repleased the thermostat 2 weeks ago. It is truth that the t-stat wasn't some great brand - it didn't have the jigle pin but a hole on it. But still I can say that it is working properly because the two 5 cm radiator hoses have different temperatures and thus the coolant is not circulating in the radiator. I guess the engine is just too big to warm up for a few miles or in your case it never gets warm because of the low surrounding temperatures.
Also do you have the belly instaled, mine is removed right now. This may also have some influence.
I am thinking of installing some piece of carton box infront of the radiator to prevent the direct contact with cold air.

Some more professional opinions will be helpful here! Thanks guys!

thats 3" shorter than the radiator on all sides and place it in front of it..until I can do the tstat.

I also want to put one. So I guess I must place it between the radiator and the AC-radiator (or is it called AC condenser?).

You may not need t-stat change. Why don't you check how warm the big hoses on the radiator get? If there is a difference then the t-stat is ok. I am giving such an advise only because I recently changed mine and I know that it is a lot of work or expensive if you go to a repair shop.
There was a tread for t-stat change without removing the timing belt a few days ago. You may find it usefull if you prefer to change just this.

I realy wish I had an engine heater! And I am in NJ, I can't imagine how much you need it in the north. This is great stuff and saves the engine from this chilly starts...
I wonder how many Audis have this in the north states. It is worth every cent when you buy the car...

tstat is bad couse once it gets up to temp if I hit the highway itll dropdown and not come back up. So the tstat isnt closing waterflow to compensate the temp of the coolant. it doesnt sound to bad, Ive read austinados post like 6 times already..lol

is turned on, even on setting 2. And the thermostat is working fine. I am sure that you turn your heat on. I do it when the temperature gets to 60°C - this is when the arrow hits the middle of the three line-marks in the beginning of the temp gauge. The use of heating significantly affects the rate of engine warm up. And this is at about 25-30°F. I guess at 0°F or -20°F it must be twice as slow.
I believe that the fans won't turn on even with a cartboard on my car - it won't reach 90°C.

Overall after changing the thermostat I didn't see much improvement in the engine temperatures. And it still takes long even though the water is not circulating in the radiator (the lower radiator hose is cold, the upper hot). Now I am constantly driving at about 70-80°C engine temperatures. Even for long distances - 20 miles it barely passes the 80°C mark. This is quite dissapointing. I expected a huge improvement.

One more time, without beeng nasty, I would advise you to check how hot your hoses get.
Start the car, wait for a few minutes till the temperature of the coolant increases. When the upper hose gets hot (engine temp about 60-70°C on the coolant gauge) and the lower is still relatively cold or just a little warm then the t-stat is working fine. 30 minutes can save you 200-300 bucks or a few hours work if you do it by yourself. However if you have decided to change the timing belt and water pump, then of course you will change the t-stat too.

Good luck!

but I'm tellin' ya, I had the same symptoms as you describe and it was not the t-stat. The temp reading would stay on the third hash mark, then climb near the solid line, then drop down again. The thing was willy nilly and drove me crazy. My thought was the same, that it was the t-stat. Turns out after all that it was the ECT, or temperature sender. Now, even in this evil Chicago weather, the temp gauge climbs right up to the solid line and stays there. It's not a difficult part to replace, but maybe you want to go ahead and change out the t-stat. If it works, great, but if not, here's your next step. Good luck!

proof is when the temp dropped on the highway the interior heat followed suite. So the coolant really was to cold.

with the coolant issue, I have to agree, it's prolly a bad t-stat. For the record though, my gauge by no means fluctuated rapidly, it was slow most of the time from what I observed. Let us know how it turns out!

I may regret that though