1999 SL2 temp gauge (not coolant sensor)
 

Hi, my niece bought a 99 SL2 and everything seems great but the temp gauge doesn't work. I've changed the coolant sensor and nothing. The needle sits about 8:00 which is way under C. If I disconnect the sensor it goes up to about 9:00. C is about 10:00. With it plugged in it never moves no matter how much it's driven. It has two wires running to it and all connections seem to be good. When I connect and disconnect the sensor I can hear a tiny click right around the intake manifold somewhere. Can't make out where because the neighbor has decided to jack hammer his walkway up today.
Thanks for any help

Let me make sure I understand -- when you bought the car, the temp gauge was sitting at 8:00. You changed out the ECTS, and it's still sitting at 8:00, right?

Yes,it's still the same. It only moves if I unplug the sensor with the key on.

READ
https://www.saturnforum.com/forum/general-tech-help-13/etcs-its-connnector-6417/

The connector looks like it has been replaced at one time. Should there be any kind of current going through the wires? Can the wires be tested?

OK -- a second question -- which connector, the one going to the sensor, or the one on the PCM ??

The sensor.

I believe that's a 5 volt signal across there

The sensor resistance should read AROUND
4.2 KOhms at 60F
7.5 KOhms at 40 F
13 KOhms at 20 F
24KOhms at 0F

Derf is correct about the voltage, and also the approximate resistance readings.

On the 1999 vehicles, there's only one temperature sensor, and it feeds it's signal back to the Powertrain Control Module (PCM).

My belief is that the only way you could get the temperature gauge to go backwards (as your original posting suggests), would be to swap the wires on the back of the gauge itself. I can't see that happening, however, unless somebody's been messing with the instrument cluster .....

Who knows what the previous owner has done. I know the engine has had a total overhaul though. Might have to look into an after market gauge. I'll see if I can get a tester on it this week.
Thanks for all the input.