audifantic

Hey No Luck on unpluging the sensors.

Even the Green Sensor when unpluged the coolant gauge still has signal.

Sensor on radiator didnt do the trick either, been all over the TT and no luck.

Could it be the thermostat? Do you think that is sticking?

theaudidoctor

previous post "highlights"

A. You need to determin if it is an elect. problem (Gauge, sensor, wiring). Or an actual overheat situation (coolant level, thermostat, elect cooling fan system prob,radiator, etc.).

Now, I thought you did this. But it's never a bad idea to double check. Check with your temp gun. If you are shooting around 200f while the gauge is showing overheat, you are not overheating. This would eliminate your susspected thermostat and indicate an elect. prob.

B. You should find G2 that controls the gauge.

I don't have a late model TT to look at but I belive G2 and G62 are seperate sensors. On many of the late model audis (the 2.8 for instance, and a 2002 <2001 they are seperate> 2.7T) G2 and G62 are together. It is a four wire blue sensor, blue connector wired as follows; #1 VIO, #2 BRN/WHT, these are G2 for the gauge. #3 GRY/YEL (or GRY/GRN), #4 BRN/BLU these are G62 for the engine. If this is what you have and not a 2 wire green sensor (or black) with a green connector, this is the sensor. And when you disconnect it the gauge should come down. The wiring diagram shows the 4 wire sensor, but the wiring diagrams are often wrong. If you do in fact have a 4 wire, you already changed it, move on. And the gauge should have come down when you disconnected it, and you said it didn't, so I am going to assume you have seperat sensors.

One thing to keep in mind that I did not mention. On a normaly operating system the gauge works as you would susspect upto a certain point. Then once the engine reaches normal operational temps, the gauge reads in the middle and remanins there throughout a temp range. Should the temp increase and depending how much the cluster will see how high and how long it stays there before increasing the indicated temp on the gauge. The enginears did not want to "worry" the driver with needle fluctuations if it was within a certain temp range and timeframe.

In summery, it really sounds like you have a cluster problem based on your posts. You determined that it was not overheating with your temp gun (I am assuming while gauge showed hot), that the cluster was seeing the correct temp in the measuring blocks in the address word #17, inst cluster (again assuming while the gauge showed hot). If all the other gauges and funtions of the cluster seem normal... I think it's a cluster.

Now writing that last paragraph I thought of one last thing you could try (there's more than one way to skin a cat). With a cold engine start the car, hook up your scanner, go to #17 inst cluster, go to the channel for engine temp, now monitor the value block and drive the car (better yet have someone else drive the car). The value block and gauge reading should corrilate. If not, you have a cluster issue.