Temperature Guage Problem

My temp. guage has been working fine up until today. I can turn the key over without cranking the vehicle, when it has ran for awhile, and the guage rises. When I crank the vehicle, however, it buries below 100 like it is not working. If anyone has experienced this, please let me know how to fix it. I am thinking it is the coolant temp. sensor, but just want some input before I take the little effort to replace it. Thanks.

there a gauge sensor on the driver side of the block with 1 black wire before you replace that sensor tap the wire on a ground source with the ingition on. See if the gauge moves if it does its the gauge sensor. If it doesnt then its your manifold temp sensor.

entrylight, what model year Suburban was (is) having temperature gauge troubles? Have you fixed it? What was the solution?