Can '64 Dart Temp Gauge Be Adjusted?

RedFish said
You need nearly zero resistance between the body of the sender and engine block and neg' battery post. Too much teflon tape on the senders threads, etc,, can increase resistance.
A better guess... the gauge voltage limiter is the problem, your fuel gauge reads low also although you dont know it. In most early panels the limiter is inside the fuel gauge or temp gauge. that gauge has a slither of metal on the back of it that provides a ground for the limiter to the panel. Panel mounting screws link the ground path to dash frame. So its a daisy chain of metal to metal contacts from one end to the other.
Other members have pulled the fuel gauge to clean the contact or simply snugged up all the gauge mounting nuts that have loosened over time. Limiter and gauges work right again.
Adding a dedicated ground wire to the instrument panel insures a good ground there and can even make dash lighting bright again. Hope this helps

BobW said
My gauge reads right at the bottom end of the "operating range" scale most of the time. Infrared temp gun on the T-stat housing reads ~184, and rgw tenp sender read ~181. If I let the car idle for a whille after driving it the gauge goes up about 2 needle widths, and the t-stat housing reads ~190-192.
I'm planning to pull the sender and using my camp stove put it in water as I bring it to a boil, monitoring water temp and marking the gauge reading.

Yesterday I drained the coolant to flush the system and replace the antifreeze. While the system was empty I removed the temp sender and hung it in a pot of water over my camp stove. I also ran a ground wire from the battery to the sender body. Used a cooking thermometer to read the water temps
The marks on the tape indicate 170*, 180*, 190* 200* and 210*. They're a little indistinct, my wife has Parkinson's.
If you were to look where the needle would intersect with the temp gauge scale, I consistently run at the first line "operating range", which correlates with my 180* mark. I get the same 180* on the thermostat housing using an infrared thermometer. The highest I've seen in stop & go traffic on a 95* day is around the 190* mark.
Now I have satisfied that the sender & gauge work and seem to be fairly linear, but appear to be about 1/2 the scale of the gauge.
Does this indicate, or be consistant with, a bad IVR?