2001 Chrysler Van No Heater

a/c ok means fan ok. Where is your sight or test for good coolant flow? If it is ok going in the box and ok coming out of the box(at the firewall) there is a control system problem. The door that moves to direct the heat is inop. or the blend door that regulates temp is not operating. If this a completely electrical and electronic control system, it must be checked with a small computer. If it uses cables one of them is maybe bad or has come unattached. Take the control panel out and check the cables.
If when you have the A/c on and you turn the switch to heat it should blow cold air out of the bottom. If it does the mode door system is ok. Now try to make the air hot by turning the temp lever or swith and if it stays cold the blend door is not working. There are two types. If it is all electronic, check the fuses and scan the BCM so you can repair. Use the scanner to operate the system and thats how you can tell if it is a problem other than the computer. It is not very serviceable any other way if it is electronic.