'04 Tahoe w/84xxx miles and using BG Products coolant. Last week during cold weather I noticed the temp gauge did not go to 210 deg as usual. Only went to about 190. Even warmer days at about 60 deg the gauge still reads the same at about 190. Before changing the thermostat where is the best place to point a lazer temp gun to get a accurate reading on the coolant temp ? Or, when it is lower than freezing the spedo needle hardly moves right until the truck is warmer inside then is ok. Could the motor on the temp gauge be part of the problem ? Would like to try the temp gun reading first. Thanks. *BW*

 

I'd say try the t-stat housing, but w/o a reference reading from when the gauge was reading 210*, not sure how accurate it will be cuz I read where the laser temp. readers are sensitive to the surface reflectivity.

 

Shark is right the temp is affected by the reflectivity, and unless your gauge is calibrated to a know standard its true accuracy is questionable.
I would speculate that the external temp of the T-stat housing would be lower externally compared to internal temp...10-15 degrees would not be unreasonable.