Temp gauge issue
 

Just bought an 04 ar. Temp gauge intermittently goes dead. Any ideas ?

Coolant temp sensor. Very very very common. Original was black, new are green. Get new o ring as well. get a sensor made by Elath, they do factory oem. Others are crap. All the std parts places carry them. Tons of write ups on the forums. They all go bad every four or five years. Bad cts also will screw up your fuel mixture and hard starting. Not hard to replace but a bitch to get at. It's at the back of the engine under lots of stuff.

Get it fixed, does a lot more than temp gauge. Search the audi forums for DIY write ups.

Thanks for the information The guy that I bought the car from had The engine steam cleaned. It seems though now that it is dried out it is functioning properly. I will keep a close eye on it and decide what to do.

It is a cheap part ($20-$27 at Audi dealer), considered to be among the cheapest Audi parts... Access is not easy, but can be replaced in 30 minutes. As others have said, be sure to replace the rubber O-ring with it.

If you have trouble starting the car, ever, with no codes, this should be your #1 replacement part.

Also, I doubt engine washing affected this sensor, so don't be surprised if the issue pops up again shortly.