Has anyone else had their coolant/water temp gauge fluctuate?
 

Mine sometimes is working, sometimes isn't. Also, does anyone here have an aftermarket water temp. gauge with numbers rather than just the stock C---->H ?

you can display the actual temp. value on your climate control LCD. Article in Tech section.

Yep,when my thermostat went bad on my 97 2.8.

Found it. Thank you.

I dont' know how valid that test is. I used my VAG COM to read the ECT and ....
 

while the climate control would tell me it was 90c, the engine coolant temp sensor was reading 70 or so, gradually getting up to 90. I tend to believe the ECT reading, because it was matching the guage (the same sender signals the guage, and the ECU) reading, and matching heat output from the dash. As the temps increased on the guage and ECT reading, the heat form the dash got much warmer. All the while the CC was showing 90c. Odd. BTW, the CC uses it's own temp sender, so perhaps it's a little optimistic?

btw, on my car, the code that displays the coolant temp. is 49, and
 

not 51, like that article suggests. Maybe it's because I have the newer version of the CC unit. When I check code 51, it constantly displays 90C - I do not know what that is.

When I use code 49, it follows the movements of the coolant temp. gauge. The temp gauge starts moving around 65C, and reaches middle (the dead range) at around 85C. From that point on, the needle is programmed to stay in the middle, so even though my climate control shows frequent small fluctuations betw. 87C and 92C, the gauge in the instr. cluster sits dead in the center.

Interesting. I'll have to look at 49..

Having the same problem (more).....
 

I have the same problem, sometime the gauge works great and other times is drops down. I really thought it was the thermostat but after teting with the CC, I'm pretty sure it's not. I think the sensor is out or has a bad connection. If I unplug it and then re-plug it the guage works great for a bit then goes back to doing it's thing.
I know the CC was a different sensor because if I unplug the ECT sensor the coolant gauge goes to C but the CC display reads normal.
My bet is the ECT sensor.

Alex M.