Coolant Temp Gauge
 

I have a 2004 Avalanche, and a few months ago the coolant gauge started acting erratic. I thought it might be the stepper motors so I replaced all of them as well as swapped the bulbs for red ones. All of my gauges worked except for the coolant temp gauge, it was behaving the exact same. I tried again with two additional new steppers with no change. I plugged in my scanner to check the coolant temp and it was within normal range, and I could watch it rise and fall with time. I ran tests on the gauge cluster and all of the gauges would sweep except for the coolant temp. My uncle has a few GMT-800 trucks so he let me borrow a gauge cluster to see if it would function, and all gauges worked. Im not sure what to do as I really dont want to spend the money on a new gauge cluster. Does anyone know where I should look next?