Originally Posted by gcvt
Originally Posted by E350
Buy this Wiring Diagrams E-Series book on ebay for your model year van (as well as the Ford Workshop Manual E-Series Volumes 1 and 2 for your model year van
"JWA" would say the same
Absolute he would!
Without beating that horse more an EVTM is invaluable for anyone DIY'ing on their factory wiring systems. I've had the Workshop Manuals (which are physically h-u-g-e BTW) but didn't find them overwhelming helpful because often times they lay out a procedure which directs the reader to use a specific tool without alternative tools also listed. This is just me---some might find them very beneficial.
Under that same trim piece at the lower portion of the B-Pillar (behind driver's seat) there are a number of used and unused connectors which can be incorporated into a build out. These have power or control function connections that can operate factory-type additions or if you're clever can made part of various levels of simple or sophisticated circuits in the rear area.
As an example I installed a rear aftermarket heater using portions of the unused connectors and power available at that location.