I wonder if mine is reading low? Perhaps the 120K, 27 year old sending unit is out of tolerance?

With all new hoses, new 180 degree thermostat, new pressure cap and properly functioning fan clutch, when at it's operating temperature my gauge needle rises to the first mark past the "C" end.

Is this about right?

Sounds right. In the 83 with the water temp at 195 which is verified by the laptop and sender for the EFI, it sits about 2 ticks under half. 15 degrees less would put it barely in the operating range.

Install an supermarket one if your worried or get a new sending unit. My 5th ave doesn't move far on the gauge either

My shorty runs at the 1/4 mark. Originally with the /6 it ran at the 1/2 mark.

I'll prolly replace the temp sending unit, just for da hale of it, to relieve my own mind's question on this issue. The part is cheap enough and not TOO hard to get to.

Thanks to you guys for your quick replies.

stock guages are at best a guess anyway.

all of my mopars have had gauges way on the low side after the have a few yrs on them.

install a good mech guage and then you can compair each other to keep in check if you starts to read different so should the other.

thats how I use my gauges in the 440 truck. stock and a mech set and watch both for movements.

On the one wire thermistor temperature sensors
the circuit is completed through the grounded frame and block.

As everything gets old and corroded,
the ohms of resistance goes up
and the gauge reads low.

Cleaning everything up,
or attaching a new ground wire
from near the sensor
to near where the gauge is grounded
may get the reading back near correct.

If you have a long electrical wire jumper with clips
you can quickly test if a new ground would improve things.

Notice on the newer vehicles the thermistor sensor has two wires to insure the PCM computer gets a good signal.

1994-1995 Rams have both one wire sensors for the dash gauge and a two wire sensor for the coolant temperature signal to the PCM.

Here's a pic of where my temp gauge is at normally.

I would very much like to buy a "keeper" infrared thermometer gun,
but so far everyone i have bought have not read
32 degrees F when aimed at stirred ice in water, or read
211 to 212 degrees F when aimed at boiling water.

The ones so far have been off by a lot... 10 to 20 degrees... So i have returned them.
Fluke, Craftsman, Harbor Freight no good so far.

If any one has an infrared gun that comes close on the ice/water and boil water checks please post the brand and model.

Humm. water is clear and the infrared goes thru it to read the temp of the pot the boiling water is in or the glass the ice/water is in giving a false/low reading?

I use the candy/cooking thermo and just put it in the water at the fill cap on the rad.

I also use it on the stove checking the t-stats open/close temps.

No way to get ice water to read 32 F because its not 32 F, If it was it would be solid ice. I would also agree with the boiling water, its sensing the pot and not the water..

Stirred distilled water with ice in it is about 32 with a slight correction for air pressure. The stirring is necessary and important.

Infrared radiation emits from the top of the water surface,
not from the metal pot bottom beneath it,
but you want to aim away from the sides of the pot.

Infrared does not get absorbed
or pass clearly thru
the same materials that visible light does.
( this is actually the root argument about global warming, CO2, sunlight, earths water vapor, clouds, ice)

Boiling distilled water is in the
210 to 212 F degrees range
depending on air pressure.

http://www.csgnetwork.com/h2oboilcalc.html

I would be happy with an IR gun that would read within a few degrees of correct. But ten to twenty degrees off is too much.

I have been using Type K thermocouples that have to touch the object but can withstand 1700 F without damage.
I like the old $30 Sears ones with the 18 inch long stainless steel probe and yellow handles meant for gas furnace work,
but they dont stock them in the hardware section anymore, having replaced them with a less useful pipe clamp style.

You can slip the tiny 1/8th diameter wire probe Type K thermocouples underneath the radiator hose and under the clamp with no leak in my experience

Back to the OP's question... with 180 stat and water temp verified 180+/- by separate EFI sender, my stock gauge reads at the lowest end of the operating range.

I have had consistent results with a low cost parts store gauge showing actual temperature. Installing one even temporarily would be a good diagnostic if you are really worried.

My aftermarket Equus electric gauge reads about 15* high at the 200* range. One of these days I'll figure out the resistor I need to add in series to make it accurate at running temp.

I eventually had to verify with a candy thermometer in the radiator neck (once the thermostat opened). This was also after I characterized two other temperature sensors, and they read the same as the candy thermo.

Counting from the "C", my '85 runs just before the 4th line, not sure what that is in degrees.

on an "idiot" temperature gauge with no numbers,
i would guess that when the coolant is at or just above the thermostat setting ( maybe 180 F)
the gauge should point one marking past the far left side.

when the coolant is at 260 degrees,
which is the boil over point for
50/50 ethylene glycol- water mix
at a pressure of 16 psi like most radiator caps,
then I would guess that
the gauge needle
should point at far right.

this would put the center of the gauge reading at
220 F degrees,
which is the temperature at which most viscous clutch radiator fans "lock up" and make noise

an alternative strategy would be to put
190 degrees
in the center of the gauge
because when driving at light load
in average air temperature
that would show the needle just left of center and
indicate
"normal, no worries"