In your own thread on your issue you said that the computer reports a normal temperature. I wouldn't worry about what your dash says right now. I did post in your thread Temp Gauge on Dash
a test you should try first.
As I stated before (I think), I tested my ECT in the following manner:
1) disconnect the ECT
2) connect resistances 1400, 93, and 55 ohms in turn and observe guage
3) guage should read min, mid, and max temperature.
This tested out just fine. 1400 ohms is for 40°C, and the min in the guage is 40°C. 93 ohms is for 120°C, and the exact mid positon is 120°C. Likewise for the max. Anything that would increase the resistance would, in fact, lower the temperature. Any corrosion on the terminals could account for this.
What I didn't realize before is that although the computer and guage use the same thermistor, they use different
pins. The computer uses pins A and B so that it has it's own ground. The guage uses the threads as a ground. I used teflon tape on the threads, and I don't believe I left any threads with no teflon. The teflon could be causing an increased resistance to ground which would lower my temperature reading some what. Because the computer uses its own ground, the temperature reading is normal. I'll have to jumper the thermistor to ground somehow and see if the guage readings return to normal.
The installation instructions for the ECT did say to use a thread sealant. I'll bet teflon doesn't allow enough metal contact for a good sensor ground. I'll bet anything I've found the problem!