Is this the oil pressure switch?

[Ed88]

Ok so I found this plugged into a socket on the back of the intake just hangin out. I assume it goes in the place I circled in red? It's just to the left of the distributor

 

[Daniel Anderson]

Mine is a 1988 D100. I believe the wiring harness was black and white and it attached to the oil instrument switch/guage and it was located where your red circle appears. The green part on your switch I haven't seen. It make be broken. Mine was one piece. I replaced mine with a guage from Princess Auto as I was getting erroneous readings on my turns when driving.

 

[nikwho]

That was your oil pressure switch. Looks to be broken in half. Perhaps from a timing adjustment, rotating a wrench back there around it. Those 30+ year old plastic parts get brittle.