In a 1993 GM 2500 Vandura van, the rear air conditioning unit (if equipped) is typically located
under the rear seat or in the rear cargo area, often integrated into the floor or side panel. It's not a visually obvious unit like the one under the dash. You'll likely need to remove some interior panels or possibly even part of the floor covering to find it.
Because the exact location can vary slightly depending on options and specific model, carefully checking wiring diagrams or a shop manual for your year and model is the best way to pinpoint it. A good parts diagram could also be helpful.
