Coolant thermometer broken?

[js]

Something funny is going on here - the other day I was driving around(Houston) and the coolant temp gauge didn't move for about 15 min while driving on the highway - Then slowly it started to creep up to the middle where it usually is. So I figured the engine took longer to warm up... Then today, driving home after dinner, the needle was in the middle and then, half way home the needle dripped to "C" all the way to the left, and stayed there the whole way home. Everything else on the car is working great (love this weather!) I just put in the TT BPV about 2 weeks ago, do you think that I knocked the coolant thermostat loose or something? Where is the coolant thermo located? TIA jason 98 Casablanca White 1.8 TQMS, APRv3, TT BPV, 17"A8 5 spoke wheels with Nitto 450's

[2.7tDallas]

make SURE you take a picture of the thing oil temp up, and cooland temp down, e-mail or print it out and give it to the tech. Sometimes the thing will not throw a code, so they will call it inmtermittent and if they do not see it, they will not fix it

[hurricanesteve]

My t-stat was sticking open a little, but it never showed that cold...that gauge on the dash is actually closer to an idiot-light...straight up is actually a range of about 15 degC, so if it doesn't get there, you're either really running cold or it's broken.

Two coolant temperature sensors, one on the back of the engine...little blue or green plug just behind the back of the intake manifold...this one reads out in VAG-COM as coolant temperature. The other is on the lower driver side of the radiator...this one can be accessed through the HVAC diagnostics at location 49c (use the AW FAQ to get into diag. mode, but ignore the addresses in the FAQ, last time I checked, they were wrong...49c is the right address).

Compare the numbers at cold and at operating temp. if they differ significantly, you got a bad sensor, if they are the same, your t-stat is probably stuck open.