[T2] Engine Ground voltage drop under load, please help diagnose.

[MUTS]

Did you check that there is CLEAN metal under where battery ground strap 
fastens to steel body? In my 78 it's a simple screw holding it to the 
body. Also make sure alternator pathway is clean- like all those ring 
terminals going to starter.  I have a vague memory of one should  check 
resistances in pathway.  When a big load like headlights is turned on, I 
thought some voltage drop is normal; you must be above 13.2 to have a 
net charge going to battery, and a resting voltage of 12.6-12.7 in a 
healthy battery when bus is sitting.

MUTS  = Michael's Ultimate Thumb Saver oboe, clarinet support
93 Chevy Roadtrek 210P
78 VW Westfalia Camper