I'm having trouble with the ECT warning light coming on in my a6 c4. The coolant gauge and the Channel 51 on my climate control diagnostics seem to be working and show the correct temperature. Coolant flows throught the system and gets warm, but doesn't go over 90 and engine doesn't overheat. On the climate control diagnostics channel 26 on the other hand shows a value between 002 and 004 while driving. Where does it get it's information from? I assume it's supposed to show resistance numbers, and this low number means some sensor doesn't work properly, but I've exchanged a couple with no luck and even two local repair shops couldn't find a source for the problem. The AC compressor doesn't switch on when the warning light is on, so it's a major nuisance in addition to the ever blinking light in the dark, even though there's no overheating problem.

 

Well actually the channel 51 gives false data also, it has just fooled me. When I turn the power on it starts climbing slowly even without turning the engine on, and never goes past 90. The weird thing is the ECT warning light doesn't go on with old defective multisensor, but then the engine doesn't run too good and there's a smell of gasoline everywhere. I've tried two new parts with the same result here, and the repair shop checked the wiring. Next I'm switching the coolant tank sensor.