O.K. I'll not suggest Anyone Torture themselves by testing CONTINUITY between
the Ign. Sequence Terminal (on the Backside of the Ignition Switch) and the
opposite end of the VERY Same Wire at the PreGLow relay.

Unless,the Ign. Sequence Cable is dependent upon the PreGlow Relay's GROUND WIRE being:Clean Bright and Tight !
[IOW No Ground...for the Ign Sequence to operate against.]

If You've got a Funky Ground for the Pre GLow ReLay,It'll do Funky things!
It does have it's own SEPARATE grounding Point.

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'84 300SD sold
124.128