Remove the passenger side plastic lower dash trim panel then the metal support structure that doubles as part of the anti-submarine crash "protection" feature. Remove drive motor.

Next remove the 7-9 7mm hex head screws from the outer heater coil cover, somewhat forcibly yank it straight out, bending it slightly so it comes free. This is best done when the van interior is at least 50*F---the case is flexible enough for removal when its warm, not much lower than 50*F

Its important to pull straight out because the case has a drain leading through the other half of the case to the inside of the engine bay. Here's some photos, no particular order:

 

Thank you.