Hello and welcome to Justanswer!
Your van doesn't use a heater control valve to stop coolant flow to the heater core. The NS body style vans (starting in 1996) didn't use these valves. The heater hoses are plumbed straight from the engine to the heater core and there is constant flow any time the engine is running.
If you look up "heater control valve" for a 1996 minivan and read carefully it says heater core, and the part number it gives is for the heater core, along with the 2.0 hours of labor to replace it. (I just checked to see what they were saying, because these vans have no heater control valve).
Chrysler hasn't used heater control valves on almost any vehicle since the mid 90's, they aren't needed. Coolant flows through the heater core at all times the engine is running. The temperature of the air coming out of the vents is controlled by electronic actuators to divert the air through the a/c evaporator or the heater core depending on setting. If you are running the a/c it simply doesn't route the air through the heater core.
Does the heat blow ice cold or at least a little bit of warmth?
Have you checked the coolant level?
With the van hot either from under the hood or from under the driver's side dash, feel both heater hoses and see if they are both just as hot as the top radiator hose, or if one hose is cooler than the other.
I would try to flush the heater core if the heat seems weak (if it's ice cold air you probably have a deeper problem than the heater core being plugged). I would flush directly at the heater core with a garden hose. You can remove the hoses from it and then use a couple peices of bulk hose slid onto the heater core tubes along with your garden hose. Run the water in one direction until the water comes out clear, and then run the water in the other direction. Do this a couple times each direction until it's clear again. Then reinstall the heater hoses, bleed the air from the cooling system by running the engine with the radiator cap off until the engine is full hot and no more bubbles come out, and then see if you have heat or if it's at least better.
You're welcome, and good luck. Happly holidays to your too!