from the red book….
btw… VOM reading grounds across a wire with stuff connected at each end is dicy…
ever try to weld a copper pipe fitting after closing a main water valve …? . residual water …from the other end of the distribution will flow back and cool off any efforts to weld in a new fitting … same issue with electricity /grounds they flow both ways .
same for that vacum switch wire …. sometimes grounded by the vacum switch itself or…. at the other end …grounded by the points simply doing their job
or worst… grounded by intermittent grounding due to worn out insulation in some hidden nook or cranny between the switch and the point set for the lower cyl coil.
if Fleetwin’s excellent suggestion to disconnect the switch does not work …. disconnect the culprit wire at the points and retry… if the issue clears up I would closely inspect that wire between the switch and points
Joining AOMCI has priviledges 🙂
