Just bought a '13 Ram 1500 Express Black with 5.7 Hemi.....Driving home notice heat isn't hot, it was blowing cold air. Added Coolant figuring it might be low....no change. Found I could squeeze the radiator hoses without effort. Bought a new cap, improved pressure. No leaks seen. No wetness noted in the cab. I am thinking thermostat now....trying to decide between the 180 degree or 203 degree thermostat. What is the deal. My truck has no over heating problem....Gauges reading perfect Coolant-185*F. No check engine lights. Engine seems to be running like a top....being new to me....she still has power gets down the road fine. I drove it 100 miles home and "no issues". I did notice after horsing it....it blew more heat....my thought as serpentine belt spun the water pump it pushed/circulated the warmer coolant through. Meaning my thermostat is stuck open, and not opening and closing like it should.

 

single or dual zone HVAC?

 

Single zone heat.

i changed t-stat. Still no heat. Still i dont see any leaks, waterpump was full, no white smoke, oil looks good...temps are all running with in ranges....no overheating.

Next thought is heater core is clogged??? Any other ideas??

 

Blend door issue?? What are temps like on the inlet/outlet hoses for the heater core?

 

Do you have a three way coolant valve. It has a wire harness plug to it. it has three hoses to it and also supplies' the heat for heater core.
I changed out my Radiator, Water pump put in a new 210 degree thermostat and new hoses and so on.
I also replaced the three way valve and after checking the plug found the ground bad. After correcting, valve works fine. Heat works fine. Hope this helps.