I have a 1999 chrysler town and country that the air conditioning stopped blowing cold air even though the system is fully charged. My question is if I loaded my van with a heavy load could the lowering of the van pinch the drain line closing it off backing the system up therefore suppressing the a/c system from producing colder air.
That's a new one. If the drain tube gets blocked with debris the condensed humidity will back up into the drain pan and slosh onto the front passenger's feet.
The refrigerant hoses are really tough and you would have to work really hard to pinch or kink one of those. Also keep in mind nothing on the body has any idea how heavily-loaded the van is. Just the wheels and suspension parts move up into the wheel wells.
Due to suspension travel, the van will go up and down over bumps in the road and from being loaded. It is designed for that. A more common problem is a stuck "H-valve" but those usually acted up soon enough to be replaced under warranty.
Another thing to look at is if the system stops blowing cold after working fine for about half an hour or longer, it could be getting too cold and the condensed humidity is freezing into a block of ice that blocks air flow. All AC systems regulate to keep the evaporator from going below about 40 degrees. When freeze-up occurs, usually it's related to a mispositioned temperature sensor.