Not a great pic, but you get the jist. This one has a vacuum line nipple plugging the vacuum port. It's been relocated.
I believe on the diesels through '86 it was mounted on that plate fastened to the top of the passenger side plastic wheel well.
Paul
It's the rusty thing to the left of where the alternator wires are in this pic.
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I just looked mine over real good and the only vacuum gizmo on the right fender is a plastic ball-looking thing, about the size of a croquet ball, with only a vacuum-line going to it and NO wires.
From that multi-port manifold, just over the A/C blower, I followed each line and none go into anything that also has electricity.
The reason I was wanting to find the low-vacuum sender is that I recently replaced both of my vacuum-gauges with matching new ones that match the rest of my many gauges.
I added red LED indicator-lights in the panel for each gauge and have a couple of those annoying seat-belt buzzers that I intend to wire into the low-vacuum warning switches, such that the red light will come on and the buzzer BUZZZZZZZ, whenever a low vacuum situation presents itself, more for the cool factor, than any real reason.
I am going to take loose the main vacuum-line and see if my factory-original light even comes on; I have had this truck over twenty years and I never removed any of that stuff; if it is gone, it got removed when the truck was fairly new.