Dash Temp sensor

[dropt_98]

I've been having some odd cooling issues with my truck lately, the temp gauge on the dash likes to go from cold to op temp, then back to cold again. Sometimes hovering in between. It never reads hot, so I'm not concerned about overheating, but I wonder if either the connection on the dash is loose or the sensor itself is shot.

I have an aftermarket water temp gauge on my pillar and I would love to wire it up, but I'm not sure which of the 2 sensors is for the dash. One is gray, one is brown. I haven't had much luck figuring out which is which. Any ideas? Thanks!

 

[Shawn]

My first 2 guesses are bad connection/wire or bad gauge itself.
Easy thing to try is open the hood and make sure all the connectors on the engine are fully plugged in.

 

[dropt_98]

I've already checked the harness, swapped sensors, and I've come to the conclusion that its probably the gauge cluster. They are prone to shorting out. I'd like to just unplug the dash sensor and use my aftermarket gauge, I just don't know which sensor is for the dash and which is for the ECU...Any ideas?