Hello I have a 95 k2500 with the 5.7 My issue is when the truck is idleing the heater works great. The temp gauge reads right below the 210 degree mark. When i drive roughly a 1/4 mile down the road the temp drops to halfway mark from 100 to 210. It will warm back up to below the 210 mark and then drop again. This is telling me that the tsat is working. While the temp is fluctuating I have very little heat. Luke warm is hot compared to what i have. I have replaced the tsat twice and have bleed the system correctly . Truck has new radiator water pump and hoses. I did not have this issue last year. I have tried covering the radiator with cardboard and that doesn't help. I don't know if the fan clutch could be causing this but at this point I am grasping at straws. Any help would be greatly appreciated.