So...just for kicks....and becuase I'm a geek. I took a spare factory temp gauge and sensor from my '93 ShagRunner and wired it up on the bench. Then I applied heat and compared the gauge readings to an infa-red temp sensor I have.....just to see what it all would do....

The method was pretty crude and, I'm pretty sure when I was taking the temp readings I was actually measuring the temp of the surface the sensor was laying on and not the temperature of the sensor itself. Tomorrow, I'm gonna re-do this experiment with the sensor in water and using a thermometer for more exact readings.....but...

The gauge moved smoothly and evenly from 100 to 140 degrees, up to the mid point on the gauge face. From 140 to 210 degrees the gauge sat at the same spot. This is the place this gauge would go to normally. No matter how hard I was beating on the truck, or how hot (or cold) it was outside, the gauge always sat at this spot. Then, from 210 on the dial moved up and quickly....I think it was pegged at 230 degrees.

I also had an ohm meter wired into this setup. Even while the gauge sat still at the mid point, the resistance was changing steadily with the temps.

Based on this, it would appear that the temp factory temp gauge is infact a true idiot gauge. Tuned only for a certain range. As long as it's within that (very wide) range, it always reads the same.

Like I said, This first try was a pretty crude experiment. And, I'm going to redo this experiment tomorrow and try an get some better temp readings. I suspect the temps I was reading with the infa-red sensor were actually low (as in the sensor was much hotter).

Having had the truck for 10 years now and watching that gauge, I kind of figured this was how the gauge would work...I'm just surprised at how wide the range was.