I don't get it

[Skunksmash]

So I'm rewiring my new digital water temp gauge, to work inside the stock gauge cluster housing. So to test before I put it back in the truck, I hook the gauge up to a 12v power source. Somehow, with no sensor, its reading accurate air temperature. It was 68 degrees in the shop, and that's what the gauge said. I look over at my thermometer on the wall and its right at 68 degrees. The gauge is soldered to the sender spot on the printed circuit, but there is no sensor hooked up to it yet. Weird.

If it just reads the air temperature from the temperature of the copper on the printed circuit that its soldered to, then that makes me wonder how its going to get accurate water temp from the sensor once its in the truck.

[jaredts]

It doesn't sound like its supposed to read resistance from your oem sender.  What's the make and model?

[bake74]

     Sounds to me like the digital gauge has a internal temp reader with the capability to hook up an external one that will over ride the internal one.
     At least that is how my thought process works, without testing it myself that would be my guess.

[Skunksmash]

Its just that blue digital gauge from Glowshift. Although, it does say that the minimum temp for it is 68, so maybe it was just a coincidence that it was also 68 degrees that day.

[bake74]

Its just that blue digital gauge from Glowshift. Although, it does say that the minimum temp for it is 68, so maybe it was just a coincidence that it was also 68 degrees that day.

     Now that sounds like it, it will not drop below 68 so without the sensor hooked up it just read 68.

[DnStClr]

The water temp gauge reads voltage from the sender. As the engine coolant heats up, the sender senses a drop in resistance and sends more voltage to the gauge. The gauge reads as "temperature", but it's actually a voltage signal...

[Skunksmash]

See that's what I was thinking. Made me wonder when they were both 68 though.