2006 Pontiac G6 intermittent A/C and themostat gauge

The a/c is manual. I did a test last night and eliminated the a/c as part of the problem. I reset the system and did not run the a/c, the temp gauge crashed back to no reading 20 miles or so down the road. I do like the suggestion that it may be the temp sensor. I will r/r that and see if it cures problem.

Hello,

I'm having this same problem. I have replaced the coolant temp sensor with a GM part, but the problem persists. Any other suggestions?

It responds normally most of the time, but will occasionally drop to 100 (the lowest it goes). At that point, A/C does not work and the engine fan runs. I suspect the computer does not see the temp, so for over heating precautions it doesn't allow a/c and turns the fan on

Same problem, replaced the ECT and it still happens. I can pull the battery cable, and do a computer reset, but after about 10min, the gauge goes to 100 (lowest) and the A/C quit? Very strange, anybody find a solution?

Word for word, having the exact same problem. I replaced the ect sensor and after unplugging the battery to reset the engine light everything went back to normal for a day. Ac back, temp gauge read the temp. Then after a day, light came on again, ac not cold, temp read 100 (needle does not move). Same code as before read at autozone. The only thing I haven't done it change the therm but if the therm was bad then when the gauge does decide to work it would be reporting irregular temp changes. Unplugged the battery again and reset the engine light. All is back to normal again gauge and ac working. We will see how long it lasts. Could it be the wire connection to the ect sensor?

If I remember correctly it was 128 said the engine is operating at a normal temperature and gave the following possible solutions: low coolant (but my level is full), faulty thermostat (but it is still working), or defective engine coolant temperature sensor (which I replaced but the same problem keeps arising). Since my last post it has improved, it works more often than not but intermittently that temp gauge will drop and the a/c compressor stops clicking on, sometimes it will come back in the middle of driving. Sometimes I have to disconnect the battery to get it to work right again.