I have a 2013 ram 1500 with the 4.7 litre and I have a little heat but not great I did a heater core flush and it helped a little but the heat is still not the greatest I find the heat is better when the fan is on low. If I turn it on high it gets colder. I don’t know if this a blender door problem or do I have to replace the heater core?
Blend door, has highest probability.
Heater would have to be clogged, inside the core, so no warm from the engine coolant is getting through the heater core,
From the Outside, the fins are totally caked with gunk, dust and debris, so no air from the fan is getting thru the fins, picking up heat and transferring that heat tru the vents.
Low fan speed seems best ?
Even with totally clogged heater core fins, running air aeround the warm core itself will give more heat as more air is added. While the air coming out of the heater core will not be nearly as warm, as if the fins were not cogged, open to air flow and air actually flowed past those fins, picking up additional warmth from the heater core, having a hot heater core with blown air going around it, will warm up dsaid air.;
these heater cores are not Cam shafts and teh clearances are not that damn tight. if you feel air, you feel warmth, its air getting past the heater core.
With a blend door issue, the lower fan speed, pushing air through the heatr cores fins could outwiegh the ambient col air sneaking in.
AS fan speed increases, cold ambient air increases qand that slight amount of h eater core air getting blown thru is overwhelemed.
