Maybe the evaporator core is icing up, and when you park the ice melts and releases an unusual amount of water. Most cars (not sure about the rangers, but probably) have a de-ice temperature switch in the evaporator core which shuts off the compressor if the evaporator drops below freezing. Maybe your's is faulty. Could be completely normal, though. If you don't need AC, try the vent-only or floor-only positions. That will save you some ga$.

Jim