Thanks for the great info on troubleshooting this problem (I too had a rear window that refused to open), but on further inspection I found a somewhat different problem.
The switch tested faulty but I looked at switch and noticed that the switch could not fully return to the upright position when released.
Here is the problem - the lever arm for the switch is connected to the main body of the switch through a rivet (the lever arm pivots through this rivet), BUT the one side of the rivet is closely approximated to the metal attachment bracket.
This bracket had some corrosion and placed pressure on the rivet and prevented the switch from returning from the fully upright position.
Removing the metal from the bracket (using a dremel) that was overtop of the rivet fixed the problem for good!
Thanks again for the info - hopes this helps someone else with their rear window problem.