Keith,
Turn everything electrical on in the Van.
Both heater motor's the headlamps,radio, and the blower motor's for the
AC.

Then take a volt reading off the alternator.

If it's 13.5 volts or less your alternator can't handle the load, and
it's fried.( or on the way out)

The fact that all of a sudden this is why the Van is dying at idle when
the AC is on  and you just had the AC work done to it is total
coincidence.

The ignition has a minimum voltage which it will keep the engine running
and your alternator isn't cutting the mustard.

Turn the AC off, and you have voltage.
The Van keeps running.