I thought I'd revive this thread since I'm having much of the same problems.

I have a 96 A4 2.8 FWD.

Replaced the ECT and the gauge is still wandering all over the place. In vehicles that I've owned, a bad thermostat was evident by cold cabin heat. I've got very hot air coming through the vent. The engine light also comes on, and I'm pulling the code: P0116.

Any other sensors I should look at?

 

Thats a code for a faulty signal from the ECT sensor, i think you may have gotten a bad one, or you have bad wiring going to the ecm. There are two sensors on the older A4's, after 98 there is only 1 sensor.

 

Where is the other sensor located?

 

On the radiator, the one that controls the gauge is behind the engine.

 

My '95 A6, 2.8 has two parts labeled ECT in Bentley Manuals. One is called G62, Engine coolant temperature sensor. It has just 2 electrical terminals. The 2nd ECT is called F76, Electronic Engine coolant Temperature Thermal Switch and has 4 terminals with terminal (T) being the temp Gauge controller.

From what I gather from the manual, inserting a 40 ohm resistor from ground to the (T) terminal of the 4 terminal socket connector, should give a reading on temp gauge of 230F with ign sw. on. I plan to test this myself in the next few days when I can locate F76 as I have low readings on temp gauge all the time.

The G62 does change it's resistance with temperature variations but I have not determined the purpose of this component yet. When I removed it's connector, engine ran rough and when a put my ohmmeter across the 2 terminals of this connector, engine would crank but not start. Possibly the small voltage created by the ohmmeter is causing this result.

 

i was having the exact same problem and still am. so i changed my sensor and still nothing...then i brought it to a audi expert, and said its the thermostat. so try the sensor first only like 20 bucks with shipping(nothing to loose) and if that doesn't work you know its the thermostat.

 

For the '95 A6, 2.8, futher research shows F76, the Electronic Engine Coolant Temperature Thermal Switch has 3 electrical terminals, not 4 as previously mentioned.

Here is a photo of F76 with two views.

[IMG]local://upfiles/25667/58579F240BBA429CB3339D3E52262636.jpg[/IMG]

 

recently i had a problem, when the car was hot, at high vehicle speeds the coolant temperature gauge used to go down, on low speeds or at idle it used to go up to normal reading. logicaly it may happen when thet-stat gets stuck open. i changed the t-stat and the temperature on the dash got ok, no fluctuations. take it easy.

 

i have the same problem. your saying its not the temp sensor and its the thermostat? where is the thermostat located?

 

i have the same problem on my 98 audi v6. when i run the codes it comes up that the coolant temp sensor code comes up. is it still the thermostat. the timing belt was replaced about 20,000 miles ago. i think the thermostat and timing and water was changed. i think not sure