[A4] Engine Coolant Temp Sensor

[Jim Coleman]

The question is for an 2002 A4 with 1.8L Turbo motor. What is the current
opinion on the need to replace the Engine Coolant Temperature (ECT) sensor?
Ours was acting strangely in that when starting up with a cold engine heat
would be coming out of the heater but the dash gauge would be pegged on
cold. Then It would go partway up and return to cold several times finally
returning to normal (middle of the dash gauge) after about 10 minutes of
operation. I was about ready to replace the sensor when we took the car
south on a trip to Florida where it was in a warmer climate for a few months
and the symptom went away. It  seems to work fine now. Then a letter came
from Audi stating that the ECT was now warranted to 100K miles due to
failures. We have 98,600 miles on the car now so the ECT warranty is almost
over for us. So should I go to the very inconvenient Audi dealer and get it
replaced? There was never a CEL or any other indication. Will they replace
it even though it seems OK now? If I wait, is the ECT sensor very expensive
it I have to do it myself later outside of warranty?

Some of you on the list must have had a similar symptom. What would you do?

Jim