You didn't specify what year your Ram Van is. So, I'll give you some general tips to investigate the problem.
1.) The heater is supplied with hot radiator fluid via an inlethose. In the engine compartment, this inlet hose has a water-valve block fitting on it. The valve is controled by either a vacuum line or a boden-cable. Make sure that either of these items is functioning correctly when the temp dial is turn on the HVAC control panelnear the radio.
2.) When you replaced the hoses, did you reverse the flow of the inlet and outlet hoses? The inlet hose should be the top line with the water valve. It is rather difficult to push the fluid from the bottom hose into the narrow heater-core tubes working against gravity.
3.) Is the water-valve installed backwards on the inlet hose?
4.)Are the hoses to the heater core connected to the water-pump correctly?
There are basically two HVAC units for the Ram Van series. First generation HVAC from 1971-1997 and the second HVAC generation from 1998-2003.