My thermostat (03 QC HEMI) always sits about 2-3 needle widths below the halfway point. This week I drove out about 100 miles through the mountiains and into the desert where it was about 105 OAT; still the thermostat never rose to the halfway point. I have been told that the HEMIs temps are usually above the halfway point. I think that the temp gauge shows how far open the t-stat is not the actual temperature correct?

 

Mine always runs just below the 1/2 way line.
It shows coolant temp.

 

Like lxman said, it shows coolant temp usually from a coolant temp sensor in a head. The temp gauges in most vehicles aren't that accurate...some are even just a dummy gauge that shows an overheat condition. My hemi usually stays 1/8" under the half way point..

 

Thanks that makes me feel better. I was worried that maybe the Tstat was not opening al the way. But if the guage runs off an actual temp sensor then my theory would not make any sense. Thanks again.

 

The guages are not accurate at all, most temp gauges on modern cars will just show if it's way over or way under operating range. The ECT sensor is pretty accurate and if you hook up a scan tool with live data it will show you what the temp is exactly.

 

I don't know about that dazed01????

My 03 Hemi this year, which used to run 1 needle width below half way, suddenly started to creep up past 1/2 to the 3/4 mark.
It would then go back down to just below 1/2 way.
It did this over a 5-8 minute period.
It was almost like seeing the Tstat opening and closing.
Anyhow, it wasn't "normal" for my truck to run like this, so on investigation, I found a defective Tstat.
I replaced it and the temp now never goes over, one needle width under 1/2 way.
The point I'm making is, that if it's a "dummy gauge" etc, why did I have this degree of indication that something was wrong if they can only seem to show if the temp is "way over" or "under operating temp"?

Al.

 

Most the cars I see have teh temp gauge at halfway when the coolant temp is within 180-230 or so

 

i believe a previous poster with a ScanGauge-II OBD-II reader once posted that the dashboard gauges needle positions don't seem to match up to the official numbers for coolant temperature and oil pressure the PCM computer has in its memories