Q: My 2012 ram 2500 started over heating just had my water pump replaced around a month ago. I think it's my thermostat. How can I tell?

Hi there. First check the cooling system and see if the coolant is low. Top off all fluids that are low that could cause the engine to overheat. To check to see if the thermostat is working, feel the upper and lower radiator hose on the engine. When both hoses are the same temperature, then the thermostat is open. If one of the hoses are cooler than the other, then the thermostat is not open or slightly open. Also you can look at the water temperature gauge on the dash and monitor the needle as the engine warms up. If the needle goes up and then drops a little and then continues to climb some but not get into the red, then the thermostat is opening but its sticking. If there is no change in the gauge movement and it goes to the red line, then there could be a larger issue with the engine other than the thermostat. If your engine continues to overheat after replacing a thermostat, then I recommend seeking out a professional, such as one from Your Mechanic, to help you diagnose your cooling system.