This is my first post here, but I'm not new to forums, nor am I new to my 2012 Colorado with the 5.3L. I've fixed various issues in the last few years, many of which had short circuited timelines from info here, so I wanted to share something I found in my truck that I've not yet see on the forums at all.
Over the past few weeks, I've been observing odd temperature control issues with my truck. On some days, it would fail to warm up completely on my 4 mile traffic riddled commute to/from work, and on other days, it would appear to be overheating by the end of the commute. In all cases, the actual reported temperature from my scan tool was somewhere between 170 degF and 195 degF, meaning everything was functioning completely normal.
Admittedly, before I really dug in, I got out the parts cannon and blasted a water pump, thermostat and fan clutch at it. It has 120K on the ODO, 25K of which was from me, so I figured replacing things that needed some love anyway was a good way to down sample the diag entry points.
While my thermostat definitely needed replacement due to seal deterioration, and my water pump bearings were pretty noisy, the issue persisted after the parts cannon.
One morning though, when the weather was cool, I noticed after key on that the temperature needle was already at 1/4 warm even before starting. I drove it to work anyway, and the needle was reporting hot again on arrival, while the scan tool was once again reporting ~190 degF. This is when I got suspicious of the gauge cluster.
This weekend I pulled the cluster, which took all of 10 minutes, and disassembled it with the expectation of finding a bad needle drive motor or a needle whose attachment mechanism had come loose. To my surprise, it was a manufacturing defect from the factory. Each needle drive motor has 4 solder joints where the needle is soldered to the PCB, and 3 of the 4 needle motors in my cluster had at least 1 cold solder joint from the factory. The temp needle's motor had one of the cold joints that had failed from shock/vibration, and the solder joint was making intermediate contact, causing the motor to drive the needle erratically.
I've attached a gif of a video below showcasing how the solder pin in the PCB was loose to give you guys an idea of what to look for. The fix was to carefully add a little bit of 2.2% flux cored 63/37 leaded solder to each of the pins very quickly and carefully to reflow them. The truck is completely normal again.
I hope this helps someone else get to the bottom of what appears to be a "typical" overheating issue.