The car either needs to warm up more so that the heat from the engine can be used to heat the interior of the car or a component in the heating is broken.
There are many possibilities. The coolant level could be low due to a leak in the system. The thermostat could be broken. The heater core could be plugged. The water pump could be failed. The controls in the dash could be unhooked/broken.,,,,,,,
checked antifreeze level???
No.
No
They are the same from 1994 to 2002.
No the 1999 and 2002 1500's are different body styles.
the heater blows warm air when fan is on low but blows cold air when fan is turn to higher setting
This is typical of an engine being low on coolant in the radiator, check your radiators coolant level and fill it.
It is possible that your radiator is partially plugged or the heater core is leaking coolant or the thermostat is the wrong temperature. Sorry for so many scenarios, but I have seen all of these.
You will need to get a repair manual for this because you will be pulling the dash and the complete a/c-heating box out, very complicated......................
The valves on a 1999 Dodge Ram 5.2L are not adjustable.
I have never heard of a mixer on a dodge truck.
No