erratic temp needle, 98 s70T-5 115k

[fixityourselfer]

the temperature gauge needle used to go right up to the 3:00 position soon after starting, and it would stay there steady as long as the car was on.
about 10 weeks ago, the needle began taking a drop longer to come up, and it no longer goes up all the way to 3:oo. it stops at around 3:30-4:00, even when I'm cruising down the highway. the car's fuel economy dropped by around 4-5mpg since this began happening. if the car is standing still, the needle will suddenly go up to 3:00. . .drive off, and it drops. the weather happens to be quite chilly here now(nj) if that makes any difference
in trying to fix the problem , so far i've changed the thermostat twice,(oem 87 degree & a duralast 92degree) and nothing doing. the issue continues. my coolant temperature sensor is quite new - 5-6 mos. old, the needle functioned properly before and after i installed it. i only changed it cuz my mechanic claimed that my old one was no good. coolant level is where it belongs too.

[akitawagon]

You can check the wiring and connectors for your ECT sensor.

Someone mentioned having similar issues and I think they found that the ECT wiring had frayed or was crimped, causing the problem.