Buoymaker's fourth photo is from my truck build and that Electro-Vac works great. It pulls about -11 inches of Hg which is enough to operate the wipers without the engine running. You turn the knob marked "VAC" to on, which lights up and the Electro-Vac motor only runs when the system vacuum drops to near zero.
The ironic thing is that Trico went to the trouble to design this thing when an electric motor mated to the wiper system would have worked better. Of course, that would make it obvious that vacuum windshield motors were obsolete.
Kent
